1NMAP(1) Nmap Reference Guide NMAP(1)
2
6 nmap - Network exploration tool and security / port scanner
7
9 nmap [Scan Type...] [Options] {target specification}
10
12 Nmap (“Network Mapper”) is an open source tool for network exploration
13 and security auditing. It was designed to rapidly scan large networks,
14 although it works fine against single hosts. Nmap uses raw IP packets
15 in novel ways to determine what hosts are available on the network,
16 what services (application name and version) those hosts are offering,
17 what operating systems (and OS versions) they are running, what type of
18 packet filters/firewalls are in use, and dozens of other
19 characteristics. While Nmap is commonly used for security audits, many
20 systems and network administrators find it useful for routine tasks
21 such as network inventory, managing service upgrade schedules, and
22 monitoring host or service uptime.
23 The output from Nmap is a list of scanned targets, with supplemental
25 information on each depending on the options used. Key among that
26 information is the “interesting ports table”. That table lists the
27 port number and protocol, service name, and state. The state is either
28 open, filtered, closed, or unfiltered. Open means that an application
29 on the target machine is listening for connections/packets on that
30 port. Filtered means that a firewall, filter, or other network
31 obstacle is blocking the port so that Nmap cannot tell whether it is
32 open or closed. Closed ports have no application listening on them,
33 though they could open up at any time. Ports are classified as
34 unfiltered when they are responsive to Nmap's probes, but Nmap cannot
35 determine whether they are open or closed. Nmap reports the state
36 combinations open|filtered and closed|filtered when it cannot determine
37 which of the two states describe a port. The port table may also
38 include software version details when version detection has been
39 requested. When an IP protocol scan is requested (-sO), Nmap provides
40 information on supported IP protocols rather than listening ports.
41 In addition to the interesting ports table, Nmap can provide further
43 information on targets, including reverse DNS names, operating system
44 guesses, device types, and MAC addresses.
45 A typical Nmap scan is shown in Example 1. The only Nmap arguments used
47 in this example are -A, to enable OS and version detection, script
48 scanning, and traceroute; -T4 for faster execution; and then the
49 hostname.
50 Example 1. A representative Nmap scan
52 # nmap -A -T4 scanme.nmap.org
54 Nmap scan report for scanme.nmap.org (74.207.244.221)
56 Host is up (0.029s latency).
57 rDNS record for 74.207.244.221: li86-221.members.linode.com
58 Not shown: 995 closed ports
59 PORT STATE SERVICE VERSION
60 22/tcp open ssh OpenSSH 5.3p1 Debian 3ubuntu7 (protocol 2.0)
61 | ssh-hostkey: 1024 8d:60:f1:7c:ca:b7:3d:0a:d6:67:54:9d:69:d9:b9:dd (DSA)
62 |_2048 79:f8:09:ac:d4:e2:32:42:10:49:d3:bd:20:82:85:ec (RSA)
63 80/tcp open http Apache httpd 2.2.14 ((Ubuntu))
64 |_http-title: Go ahead and ScanMe!
65 646/tcp filtered ldp
66 1720/tcp filtered H.323/Q.931
67 9929/tcp open nping-echo Nping echo
68 Device type: general purpose
69 Running: Linux 2.6.X
70 OS CPE: cpe:/o:linux:linux_kernel:2.6.39
71 OS details: Linux 2.6.39
72 Network Distance: 11 hops
73 Service Info: OS: Linux; CPE: cpe:/o:linux:kernel
74 TRACEROUTE (using port 53/tcp)
76 HOP RTT ADDRESS
77 [Cut first 10 hops for brevity]
78 11 17.65 ms li86-221.members.linode.com (74.207.244.221)
79 Nmap done: 1 IP address (1 host up) scanned in 14.40 seconds
81 The newest version of Nmap can be obtained from https://nmap.org. The
83 newest version of this man page is available at
84 https://nmap.org/book/man.html. It is also included as a chapter of
85 Nmap Network Scanning: The Official Nmap Project Guide to Network
86 Discovery and Security Scanning (see https://nmap.org/book/).
87
89 This options summary is printed when Nmap is run with no arguments, and
90 the latest version is always available at
91 https://svn.nmap.org/nmap/docs/nmap.usage.txt. It helps people remember
92 the most common options, but is no substitute for the in-depth
93 documentation in the rest of this manual. Some obscure options aren't
94 even included here.
95 Nmap 7.93 ( https://nmap.org )
97 Usage: nmap [Scan Type(s)] [Options] {target specification}
98 TARGET SPECIFICATION:
99 Can pass hostnames, IP addresses, networks, etc.
100 Ex: scanme.nmap.org, 192.168.0.1; 10.0.0-255.1-254
101 -iL <inputfilename>: Input from list of hosts/networks
102 -iR <num hosts>: Choose random targets
103 --exclude <host1[,host2][,host3],...>: Exclude hosts/networks
104 --excludefile <exclude_file>: Exclude list from file
105 HOST DISCOVERY:
106 -sL: List Scan - simply list targets to scan
107 -sn: Ping Scan - disable port scan
108 -Pn: Treat all hosts as online -- skip host discovery
109 -PS/PA/PU/PY[portlist]: TCP SYN/ACK, UDP or SCTP discovery to given ports
110 -PE/PP/PM: ICMP echo, timestamp, and netmask request discovery probes
111 -PO[protocol list]: IP Protocol Ping
112 -n/-R: Never do DNS resolution/Always resolve [default: sometimes]
113 --dns-servers <serv1[,serv2],...>: Specify custom DNS servers
114 --system-dns: Use OS's DNS resolver
115 --traceroute: Trace hop path to each host
116 SCAN TECHNIQUES:
117 -sS/sT/sA/sW/sM: TCP SYN/Connect()/ACK/Window/Maimon scans
118 -sU: UDP Scan
119 -sN/sF/sX: TCP Null, FIN, and Xmas scans
120 --scanflags <flags>: Customize TCP scan flags
121 -sI <zombie host[:probeport]>: Idle scan
122 -sY/sZ: SCTP INIT/COOKIE-ECHO scans
123 -sO: IP protocol scan
124 -b <FTP relay host>: FTP bounce scan
125 PORT SPECIFICATION AND SCAN ORDER:
126 -p <port ranges>: Only scan specified ports
127 Ex: -p22; -p1-65535; -p U:53,111,137,T:21-25,80,139,8080,S:9
128 --exclude-ports <port ranges>: Exclude the specified ports from scanning
129 -F: Fast mode - Scan fewer ports than the default scan
130 -r: Scan ports sequentially - don't randomize
131 --top-ports <number>: Scan <number> most common ports
132 --port-ratio <ratio>: Scan ports more common than <ratio>
133 SERVICE/VERSION DETECTION:
134 -sV: Probe open ports to determine service/version info
135 --version-intensity <level>: Set from 0 (light) to 9 (try all probes)
136 --version-light: Limit to most likely probes (intensity 2)
137 --version-all: Try every single probe (intensity 9)
138 --version-trace: Show detailed version scan activity (for debugging)
139 SCRIPT SCAN:
140 -sC: equivalent to --script=default
141 --script=<Lua scripts>: <Lua scripts> is a comma separated list of
142 directories, script-files or script-categories
143 --script-args=<n1=v1,[n2=v2,...]>: provide arguments to scripts
144 --script-args-file=filename: provide NSE script args in a file
145 --script-trace: Show all data sent and received
146 --script-updatedb: Update the script database.
147 --script-help=<Lua scripts>: Show help about scripts.
148 <Lua scripts> is a comma-separated list of script-files or
149 script-categories.
150 OS DETECTION:
151 -O: Enable OS detection
152 --osscan-limit: Limit OS detection to promising targets
153 --osscan-guess: Guess OS more aggressively
154 TIMING AND PERFORMANCE:
155 Options which take <time> are in seconds, or append 'ms' (milliseconds),
156 's' (seconds), 'm' (minutes), or 'h' (hours) to the value (e.g. 30m).
157 -T<0-5>: Set timing template (higher is faster)
158 --min-hostgroup/max-hostgroup <size>: Parallel host scan group sizes
159 --min-parallelism/max-parallelism <numprobes>: Probe parallelization
160 --min-rtt-timeout/max-rtt-timeout/initial-rtt-timeout <time>: Specifies
161 probe round trip time.
162 --max-retries <tries>: Caps number of port scan probe retransmissions.
163 --host-timeout <time>: Give up on target after this long
164 --scan-delay/--max-scan-delay <time>: Adjust delay between probes
165 --min-rate <number>: Send packets no slower than <number> per second
166 --max-rate <number>: Send packets no faster than <number> per second
167 FIREWALL/IDS EVASION AND SPOOFING:
168 -f; --mtu <val>: fragment packets (optionally w/given MTU)
169 -D <decoy1,decoy2[,ME],...>: Cloak a scan with decoys
170 -S <IP_Address>: Spoof source address
171 -e <iface>: Use specified interface
172 -g/--source-port <portnum>: Use given port number
173 --proxies <url1,[url2],...>: Relay connections through HTTP/SOCKS4 proxies
174 --data <hex string>: Append a custom payload to sent packets
175 --data-string <string>: Append a custom ASCII string to sent packets
176 --data-length <num>: Append random data to sent packets
177 --ip-options <options>: Send packets with specified ip options
178 --ttl <val>: Set IP time-to-live field
179 --spoof-mac <mac address/prefix/vendor name>: Spoof your MAC address
180 --badsum: Send packets with a bogus TCP/UDP/SCTP checksum
181 OUTPUT:
182 -oN/-oX/-oS/-oG <file>: Output scan in normal, XML, s|<rIpt kIddi3,
183 and Grepable format, respectively, to the given filename.
184 -oA <basename>: Output in the three major formats at once
185 -v: Increase verbosity level (use -vv or more for greater effect)
186 -d: Increase debugging level (use -dd or more for greater effect)
187 --reason: Display the reason a port is in a particular state
188 --open: Only show open (or possibly open) ports
189 --packet-trace: Show all packets sent and received
190 --iflist: Print host interfaces and routes (for debugging)
191 --append-output: Append to rather than clobber specified output files
192 --resume <filename>: Resume an aborted scan
193 --noninteractive: Disable runtime interactions via keyboard
194 --stylesheet <path/URL>: XSL stylesheet to transform XML output to HTML
195 --webxml: Reference stylesheet from Nmap.Org for more portable XML
196 --no-stylesheet: Prevent associating of XSL stylesheet w/XML output
197 MISC:
198 -6: Enable IPv6 scanning
199 -A: Enable OS detection, version detection, script scanning, and traceroute
200 --datadir <dirname>: Specify custom Nmap data file location
201 --send-eth/--send-ip: Send using raw ethernet frames or IP packets
202 --privileged: Assume that the user is fully privileged
203 --unprivileged: Assume the user lacks raw socket privileges
204 -V: Print version number
205 -h: Print this help summary page.
206 EXAMPLES:
207 nmap -v -A scanme.nmap.org
208 nmap -v -sn 192.168.0.0/16 10.0.0.0/8
209 nmap -v -iR 10000 -Pn -p 80
210 SEE THE MAN PAGE (https://nmap.org/book/man.html) FOR MORE OPTIONS AND EXAMPLES
211
213 Everything on the Nmap command-line that isn't an option (or option
214 argument) is treated as a target host specification. The simplest case
215 is to specify a target IP address or hostname for scanning.
216 When a hostname is given as a target, it is resolved via the Domain
218 Name System (DNS) to determine the IP address to scan. If the name
219 resolves to more than one IP address, only the first one will be
220 scanned. To make Nmap scan all the resolved addresses instead of only
221 the first one, use the --resolve-all option.
222 Sometimes you wish to scan a whole network of adjacent hosts. For this,
224 Nmap supports CIDR-style addressing. You can append /numbits to an IP
225 address or hostname and Nmap will scan every IP address for which the
226 first numbits are the same as for the reference IP or hostname given.
227 For example, 192.168.10.0/24 would scan the 256 hosts between
228 192.168.10.0 (binary: 11000000 10101000 00001010 00000000) and
229 192.168.10.255 (binary: 11000000 10101000 00001010 11111111),
230 inclusive. 192.168.10.40/24 would scan exactly the same targets. Given
231 that the host scanme.nmap.org is at the IP address 64.13.134.52, the
232 specification scanme.nmap.org/16 would scan the 65,536 IP addresses
233 between 64.13.0.0 and 64.13.255.255. The smallest allowed value is /0,
234 which targets the whole Internet. The largest value for IPv4 is /32,
235 which scans just the named host or IP address because all address bits
236 are fixed. The largest value for IPv6 is /128, which does the same
237 thing.
238 CIDR notation is short but not always flexible enough. For example, you
240 might want to scan 192.168.0.0/16 but skip any IPs ending with .0 or
241 .255 because they may be used as subnet network and broadcast
242 addresses. Nmap supports this through octet range addressing. Rather
243 than specify a normal IP address, you can specify a comma-separated
244 list of numbers or ranges for each octet. For example,
245 192.168.0-255.1-254 will skip all addresses in the range that end in .0
246 or .255, and 192.168.3-5,7.1 will scan the four addresses 192.168.3.1,
247 192.168.4.1, 192.168.5.1, and 192.168.7.1. Either side of a range may
248 be omitted; the default values are 0 on the left and 255 on the right.
249 Using - by itself is the same as 0-255, but remember to use 0- in the
250 first octet so the target specification doesn't look like a
251 command-line option. Ranges need not be limited to the final octets:
252 the specifier 0-255.0-255.13.37 will perform an Internet-wide scan for
253 all IP addresses ending in 13.37. This sort of broad sampling can be
254 useful for Internet surveys and research.
255 IPv6 addresses can be specified by their fully qualified IPv6 address
257 or hostname or with CIDR notation for subnets. Octet ranges aren't yet
258 supported for IPv6.
259 IPv6 addresses with non-global scope need to have a zone ID suffix. On
261 Unix systems, this is a percent sign followed by an interface name; a
262 complete address might be fe80::a8bb:ccff:fedd:eeff%eth0. On Windows,
263 use an interface index number in place of an interface name:
264 fe80::a8bb:ccff:fedd:eeff%1. You can see a list of interface indexes by
265 running the command netsh.exe interface ipv6 show interface.
266 Nmap accepts multiple host specifications on the command line, and they
268 don't need to be the same type. The command nmap scanme.nmap.org
269 192.168.0.0/8 10.0.0,1,3-7.- does what you would expect.
270 While targets are usually specified on the command lines, the following
272 options are also available to control target selection:
273 -iL inputfilename (Input from list)
275 Reads target specifications from inputfilename. Passing a huge list
276 of hosts is often awkward on the command line, yet it is a common
277 desire. For example, your DHCP server might export a list of 10,000
278 current leases that you wish to scan. Or maybe you want to scan all
279 IP addresses except for those to locate hosts using unauthorized
280 static IP addresses. Simply generate the list of hosts to scan and
281 pass that filename to Nmap as an argument to the -iL option.
282 Entries can be in any of the formats accepted by Nmap on the
283 command line (IP address, hostname, CIDR, IPv6, or octet ranges).
284 Each entry must be separated by one or more spaces, tabs, or
285 newlines. You can specify a hyphen (-) as the filename if you want
286 Nmap to read hosts from standard input rather than an actual file.
287 The input file may contain comments that start with # and extend to
289 the end of the line.
290 -iR num hosts (Choose random targets)
292 For Internet-wide surveys and other research, you may want to
293 choose targets at random. The num hosts argument tells Nmap how
294 many IPs to generate. Undesirable IPs such as those in certain
295 private, multicast, or unallocated address ranges are automatically
296 skipped. The argument 0 can be specified for a never-ending scan.
297 Keep in mind that some network administrators bristle at
298 unauthorized scans of their networks and may complain. Use this
299 option at your own risk! If you find yourself really bored one
300 rainy afternoon, try the command nmap -Pn -sS -p 80 -iR 0 --open to
301 locate random web servers for browsing.
302 --exclude host1[,host2[,...]] (Exclude hosts/networks)
304 Specifies a comma-separated list of targets to be excluded from the
305 scan even if they are part of the overall network range you
306 specify. The list you pass in uses normal Nmap syntax, so it can
307 include hostnames, CIDR netblocks, octet ranges, etc. This can be
308 useful when the network you wish to scan includes untouchable
309 mission-critical servers, systems that are known to react adversely
310 to port scans, or subnets administered by other people.
311 --excludefile exclude_file (Exclude list from file)
313 This offers the same functionality as the --exclude option, except
314 that the excluded targets are provided in a newline-, space-, or
315 tab-delimited exclude_file rather than on the command line.
316 The exclude file may contain comments that start with # and extend
318 to the end of the line.
319 -n (No DNS resolution)
321 Tells Nmap to never do reverse DNS resolution on the active IP
323 addresses it finds. Since DNS can be slow even with Nmap's built-in
324 parallel stub resolver, this option can slash scanning times.
325 -R (DNS resolution for all targets)
327 Tells Nmap to always do reverse DNS resolution on the target IP
328 addresses. Normally reverse DNS is only performed against
329 responsive (online) hosts.
330 --resolve-all (Scan each resolved address)
332 If a hostname target resolves to more than one address, scan all of
333 them. The default behavior is to only scan the first resolved
334 address. Regardless, only addresses in the appropriate address
335 family will be scanned: IPv4 by default, IPv6 with -6.
336 --unique (Scan each address only once)
338 Scan each IP address only once. The default behavior is to scan
339 each address as many times as it is specified in the target list,
340 such as when network ranges overlap or different hostnames resolve
341 to the same address.
342 --system-dns (Use system DNS resolver)
344 By default, Nmap reverse-resolves IP addresses by sending queries
345 directly to the name servers configured on your host and then
346 listening for responses. Many requests (often dozens) are performed
347 in parallel to improve performance. Specify this option to use your
348 system resolver instead (one IP at a time via the getnameinfo
349 call). This is slower and rarely useful unless you find a bug in
350 the Nmap parallel resolver (please let us know if you do). The
351 system resolver is always used for forward lookups (getting an IP
352 address from a hostname).
353 --dns-servers server1[,server2[,...]] (Servers to use for reverse DNS
355 queries)
356 By default, Nmap determines your DNS servers (for rDNS resolution)
357 from your resolv.conf file (Unix) or the Registry (Win32).
358 Alternatively, you may use this option to specify alternate
359 servers. This option is not honored if you are using --system-dns.
360 Using multiple DNS servers is often faster, especially if you
361 choose authoritative servers for your target IP space. This option
362 can also improve stealth, as your requests can be bounced off just
363 about any recursive DNS server on the Internet.
364 This option also comes in handy when scanning private networks.
366 Sometimes only a few name servers provide proper rDNS information,
367 and you may not even know where they are. You can scan the network
368 for port 53 (perhaps with version detection), then try Nmap list
369 scans (-sL) specifying each name server one at a time with
370 --dns-servers until you find one which works.
371 This option might not be honored if the DNS response exceeds the
373 size of a UDP packet. In such a situation our DNS resolver will
374 make the best effort to extract a response from the truncated
375 packet, and if not successful it will fall back to using the system
376 resolver. Also, responses that contain CNAME aliases will fall back
377 to the system resolver.
378
380 One of the very first steps in any network reconnaissance mission is to
381 reduce a (sometimes huge) set of IP ranges into a list of active or
382 interesting hosts. Scanning every port of every single IP address is
383 slow and usually unnecessary. Of course what makes a host interesting
384 depends greatly on the scan purposes. Network administrators may only
385 be interested in hosts running a certain service, while security
386 auditors may care about every single device with an IP address. An
387 administrator may be comfortable using just an ICMP ping to locate
388 hosts on his internal network, while an external penetration tester may
389 use a diverse set of dozens of probes in an attempt to evade firewall
390 restrictions.
391 Because host discovery needs are so diverse, Nmap offers a wide variety
393 of options for customizing the techniques used. Host discovery is
394 sometimes called ping scan, but it goes well beyond the simple ICMP
395 echo request packets associated with the ubiquitous ping tool. Users
396 can skip the discovery step entirely with a list scan (-sL) or by
397 disabling host discovery (-Pn), or engage the network with arbitrary
398 combinations of multi-port TCP SYN/ACK, UDP, SCTP INIT and ICMP probes.
399 The goal of these probes is to solicit responses which demonstrate that
400 an IP address is actually active (is being used by a host or network
401 device). On many networks, only a small percentage of IP addresses are
402 active at any given time. This is particularly common with private
403 address space such as 10.0.0.0/8. That network has 16 million IPs, but
404 I have seen it used by companies with less than a thousand machines.
405 Host discovery can find those machines in a sparsely allocated sea of
406 IP addresses.
407 If no host discovery options are given, Nmap sends an ICMP echo
409 request, a TCP SYN packet to port 443, a TCP ACK packet to port 80, and
410 an ICMP timestamp request. (For IPv6, the ICMP timestamp request is
411 omitted because it is not part of ICMPv6.) These defaults are
412 equivalent to the -PE -PS443 -PA80 -PP options. The exceptions to this
413 are the ARP (for IPv4) and Neighbor Discovery (for IPv6) scans which
414 are used for any targets on a local ethernet network. For unprivileged
415 Unix shell users, the default probes are a SYN packet to ports 80 and
416 443 using the connect system call. This host discovery is often
417 sufficient when scanning local networks, but a more comprehensive set
418 of discovery probes is recommended for security auditing.
419 The -P* options (which select ping types) can be combined. You can
421 increase your odds of penetrating strict firewalls by sending many
422 probe types using different TCP ports/flags and ICMP codes. Also note
423 that ARP/Neighbor Discovery is done by default against targets on a
424 local Ethernet network even if you specify other -P* options, because
425 it is almost always faster and more effective.
426 By default, Nmap does host discovery and then performs a port scan
428 against each host it determines is online. This is true even if you
429 specify non-default host discovery types such as UDP probes (-PU). Read
430 about the -sn option to learn how to perform only host discovery, or
431 use -Pn to skip host discovery and port scan all target addresses. The
432 following options control host discovery:
433 -sL (List Scan)
435 The list scan is a degenerate form of host discovery that simply
436 lists each host of the network(s) specified, without sending any
437 packets to the target hosts. By default, Nmap still does
438 reverse-DNS resolution on the hosts to learn their names. It is
439 often surprising how much useful information simple hostnames give
440 out. For example, fw.chi is the name of one company's Chicago
441 firewall.
442 Nmap also reports the total number of IP addresses at the end. The
444 list scan is a good sanity check to ensure that you have proper IP
445 addresses for your targets. If the hosts sport domain names you do
446 not recognize, it is worth investigating further to prevent
447 scanning the wrong company's network.
448 Since the idea is to simply print a list of target hosts, options
450 for higher level functionality such as port scanning, OS detection,
451 or host discovery cannot be combined with this. If you wish to
452 disable host discovery while still performing such higher level
453 functionality, read up on the -Pn (skip host discovery) option.
454 -sn (No port scan)
456 This option tells Nmap not to do a port scan after host discovery,
457 and only print out the available hosts that responded to the host
458 discovery probes. This is often known as a “ping scan”, but you can
459 also request that traceroute and NSE host scripts be run. This is
460 by default one step more intrusive than the list scan, and can
461 often be used for the same purposes. It allows light reconnaissance
462 of a target network without attracting much attention. Knowing how
463 many hosts are up is more valuable to attackers than the list
464 provided by list scan of every single IP and host name.
465 Systems administrators often find this option valuable as well. It
467 can easily be used to count available machines on a network or
468 monitor server availability. This is often called a ping sweep, and
469 is more reliable than pinging the broadcast address because many
470 hosts do not reply to broadcast queries.
471 The default host discovery done with -sn consists of an ICMP echo
473 request, TCP SYN to port 443, TCP ACK to port 80, and an ICMP
474 timestamp request by default. When executed by an unprivileged
475 user, only SYN packets are sent (using a connect call) to ports 80
476 and 443 on the target. When a privileged user tries to scan targets
477 on a local ethernet network, ARP requests are used unless --send-ip
478 was specified. The -sn option can be combined with any of the
479 discovery probe types (the -P* options) for greater flexibility. If
480 any of those probe type and port number options are used, the
481 default probes are overridden. When strict firewalls are in place
482 between the source host running Nmap and the target network, using
483 those advanced techniques is recommended. Otherwise hosts could be
484 missed when the firewall drops probes or their responses.
485 In previous releases of Nmap, -sn was known as -sP.
487 -Pn (No ping)
489 This option skips the host discovery stage altogether. Normally,
490 Nmap uses this stage to determine active machines for heavier
491 scanning and to gauge the speed of the network. By default, Nmap
492 only performs heavy probing such as port scans, version detection,
493 or OS detection against hosts that are found to be up. Disabling
494 host discovery with -Pn causes Nmap to attempt the requested
495 scanning functions against every target IP address specified. So if
496 a /16 sized network is specified on the command line, all 65,536 IP
497 addresses are scanned. Proper host discovery is skipped as with the
498 list scan, but instead of stopping and printing the target list,
499 Nmap continues to perform requested functions as if each target IP
500 is active. Default timing parameters are used, which may result in
501 slower scans. To skip host discovery and port scan, while still
502 allowing NSE to run, use the two options -Pn -sn together.
503 For machines on a local ethernet network, ARP scanning will still
505 be performed (unless --disable-arp-ping or --send-ip is specified)
506 because Nmap needs MAC addresses to further scan target hosts. In
507 previous versions of Nmap, -Pn was -P0 and -PN.
508 -PS port list (TCP SYN Ping)
510 This option sends an empty TCP packet with the SYN flag set. The
511 default destination port is 80 (configurable at compile time by
512 changing DEFAULT_TCP_PROBE_PORT_SPEC in nmap.h). Alternate ports
513 can be specified as a parameter. The syntax is the same as for the
514 -p except that port type specifiers like T: are not allowed.
515 Examples are -PS22 and -PS22-25,80,113,1050,35000. Note that there
516 can be no space between -PS and the port list. If multiple probes
517 are specified they will be sent in parallel.
518 The SYN flag suggests to the remote system that you are attempting
520 to establish a connection. Normally the destination port will be
521 closed, and a RST (reset) packet sent back. If the port happens to
522 be open, the target will take the second step of a TCP
523 three-way-handshake by responding with a SYN/ACK TCP packet. The
524 machine running Nmap then tears down the nascent connection by
525 responding with a RST rather than sending an ACK packet which would
526 complete the three-way-handshake and establish a full connection.
527 The RST packet is sent by the kernel of the machine running Nmap in
528 response to the unexpected SYN/ACK, not by Nmap itself.
529 Nmap does not care whether the port is open or closed. Either the
531 RST or SYN/ACK response discussed previously tell Nmap that the
532 host is available and responsive.
533 On Unix boxes, only the privileged user root is generally able to
535 send and receive raw TCP packets. For unprivileged users, a
536 workaround is automatically employed whereby the connect system
537 call is initiated against each target port. This has the effect of
538 sending a SYN packet to the target host, in an attempt to establish
539 a connection. If connect returns with a quick success or an
540 ECONNREFUSED failure, the underlying TCP stack must have received a
541 SYN/ACK or RST and the host is marked available. If the connection
542 attempt is left hanging until a timeout is reached, the host is
543 marked as down.
544 -PA port list (TCP ACK Ping)
546 The TCP ACK ping is quite similar to the just-discussed SYN ping.
547 The difference, as you could likely guess, is that the TCP ACK flag
548 is set instead of the SYN flag. Such an ACK packet purports to be
549 acknowledging data over an established TCP connection, but no such
550 connection exists. So remote hosts should always respond with a RST
551 packet, disclosing their existence in the process.
552 The -PA option uses the same default port as the SYN probe (80) and
554 can also take a list of destination ports in the same format. If an
555 unprivileged user tries this, the connect workaround discussed
556 previously is used. This workaround is imperfect because connect is
557 actually sending a SYN packet rather than an ACK.
558 The reason for offering both SYN and ACK ping probes is to maximize
560 the chances of bypassing firewalls. Many administrators configure
561 routers and other simple firewalls to block incoming SYN packets
562 except for those destined for public services like the company web
563 site or mail server. This prevents other incoming connections to
564 the organization, while allowing users to make unobstructed
565 outgoing connections to the Internet. This non-stateful approach
566 takes up few resources on the firewall/router and is widely
567 supported by hardware and software filters. The Linux
568 Netfilter/iptables firewall software offers the --syn convenience
569 option to implement this stateless approach. When stateless
570 firewall rules such as this are in place, SYN ping probes (-PS) are
571 likely to be blocked when sent to closed target ports. In such
572 cases, the ACK probe shines as it cuts right through these rules.
573 Another common type of firewall uses stateful rules that drop
575 unexpected packets. This feature was initially found mostly on
576 high-end firewalls, though it has become much more common over the
577 years. The Linux Netfilter/iptables system supports this through
578 the --state option, which categorizes packets based on connection
579 state. A SYN probe is more likely to work against such a system, as
580 unexpected ACK packets are generally recognized as bogus and
581 dropped. A solution to this quandary is to send both SYN and ACK
582 probes by specifying -PS and -PA.
583 -PU port list (UDP Ping)
585 Another host discovery option is the UDP ping, which sends a UDP
586 packet to the given ports. For most ports, the packet will be
587 empty, though some use a protocol-specific payload that is more
588 likely to elicit a response. The payload database is described at
589 https://nmap.org/book/nmap-payloads.html.
590 Packet content can also be affected with the --data, --data-string,
592 and --data-length options.
593 The port list takes the same format as with the previously
595 discussed -PS and -PA options. If no ports are specified, the
596 default is 40125. This default can be configured at compile-time
597 by changing DEFAULT_UDP_PROBE_PORT_SPEC in nmap.h. A highly
598 uncommon port is used by default because sending to open ports is
599 often undesirable for this particular scan type.
600 Upon hitting a closed port on the target machine, the UDP probe
602 should elicit an ICMP port unreachable packet in return. This
603 signifies to Nmap that the machine is up and available. Many other
604 types of ICMP errors, such as host/network unreachables or TTL
605 exceeded are indicative of a down or unreachable host. A lack of
606 response is also interpreted this way. If an open port is reached,
607 most services simply ignore the empty packet and fail to return any
608 response. This is why the default probe port is 40125, which is
609 highly unlikely to be in use. A few services, such as the Character
610 Generator (chargen) protocol, will respond to an empty UDP packet,
611 and thus disclose to Nmap that the machine is available.
612 The primary advantage of this scan type is that it bypasses
614 firewalls and filters that only screen TCP. For example, I once
615 owned a Linksys BEFW11S4 wireless broadband router. The external
616 interface of this device filtered all TCP ports by default, but UDP
617 probes would still elicit port unreachable messages and thus give
618 away the device.
619 -PY port list (SCTP INIT Ping)
621 This option sends an SCTP packet containing a minimal INIT chunk.
622 The default destination port is 80 (configurable at compile time by
623 changing DEFAULT_SCTP_PROBE_PORT_SPEC in nmap.h). Alternate ports
624 can be specified as a parameter. The syntax is the same as for the
625 -p except that port type specifiers like S: are not allowed.
626 Examples are -PY22 and -PY22,80,179,5060. Note that there can be no
627 space between -PY and the port list. If multiple probes are
628 specified they will be sent in parallel.
629 The INIT chunk suggests to the remote system that you are
631 attempting to establish an association. Normally the destination
632 port will be closed, and an ABORT chunk will be sent back. If the
633 port happens to be open, the target will take the second step of an
634 SCTP four-way-handshake by responding with an INIT-ACK chunk. If
635 the machine running Nmap has a functional SCTP stack, then it tears
636 down the nascent association by responding with an ABORT chunk
637 rather than sending a COOKIE-ECHO chunk which would be the next
638 step in the four-way-handshake. The ABORT packet is sent by the
639 kernel of the machine running Nmap in response to the unexpected
640 INIT-ACK, not by Nmap itself.
641 Nmap does not care whether the port is open or closed. Either the
643 ABORT or INIT-ACK response discussed previously tell Nmap that the
644 host is available and responsive.
645 On Unix boxes, only the privileged user root is generally able to
647 send and receive raw SCTP packets. Using SCTP INIT Pings is
648 currently not possible for unprivileged users.
649 -PE; -PP; -PM (ICMP Ping Types)
651 In addition to the unusual TCP, UDP and SCTP host discovery types
652 discussed previously, Nmap can send the standard packets sent by
653 the ubiquitous ping program. Nmap sends an ICMP type 8 (echo
654 request) packet to the target IP addresses, expecting a type 0
655 (echo reply) in return from available hosts. Unfortunately for
656 network explorers, many hosts and firewalls now block these
657 packets, rather than responding as required by RFC 1122[2]. For
658 this reason, ICMP-only scans are rarely reliable enough against
659 unknown targets over the Internet. But for system administrators
660 monitoring an internal network, they can be a practical and
661 efficient approach. Use the -PE option to enable this echo request
662 behavior.
663 While echo request is the standard ICMP ping query, Nmap does not
665 stop there. The ICMP standards (RFC 792[3] and RFC 950[4] ) also
666 specify timestamp request, information request, and address mask
667 request packets as codes 13, 15, and 17, respectively. While the
668 ostensible purpose for these queries is to learn information such
669 as address masks and current times, they can easily be used for
670 host discovery. A system that replies is up and available. Nmap
671 does not currently implement information request packets, as they
672 are not widely supported. RFC 1122 insists that “a host SHOULD NOT
673 implement these messages”. Timestamp and address mask queries can
674 be sent with the -PP and -PM options, respectively. A timestamp
675 reply (ICMP code 14) or address mask reply (code 18) discloses that
676 the host is available. These two queries can be valuable when
677 administrators specifically block echo request packets while
678 forgetting that other ICMP queries can be used for the same
679 purpose.
680 -PO protocol list (IP Protocol Ping)
682 One of the newer host discovery options is the IP protocol ping,
683 which sends IP packets with the specified protocol number set in
684 their IP header. The protocol list takes the same format as do port
685 lists in the previously discussed TCP, UDP and SCTP host discovery
686 options. If no protocols are specified, the default is to send
687 multiple IP packets for ICMP (protocol 1), IGMP (protocol 2), and
688 IP-in-IP (protocol 4). The default protocols can be configured at
689 compile-time by changing DEFAULT_PROTO_PROBE_PORT_SPEC in nmap.h.
690 Note that for the ICMP, IGMP, TCP (protocol 6), UDP (protocol 17)
691 and SCTP (protocol 132), the packets are sent with the proper
692 protocol headers while other protocols are sent with no additional
693 data beyond the IP header (unless any of --data, --data-string, or
694 --data-length options are specified).
695 This host discovery method looks for either responses using the
697 same protocol as a probe, or ICMP protocol unreachable messages
698 which signify that the given protocol isn't supported on the
699 destination host. Either type of response signifies that the target
700 host is alive.
701 --disable-arp-ping (No ARP or ND Ping)
703 Nmap normally does ARP or IPv6 Neighbor Discovery (ND) discovery of
704 locally connected ethernet hosts, even if other host discovery
705 options such as -Pn or -PE are used. To disable this implicit
706 behavior, use the --disable-arp-ping option.
707 The default behavior is normally faster, but this option is useful
709 on networks using proxy ARP, in which a router speculatively
710 replies to all ARP requests, making every target appear to be up
711 according to ARP scan.
712 --discovery-ignore-rst
714 In some cases, firewalls may spoof TCP reset (RST) replies in
715 response to probes to unoccupied or disallowed addresses. Since
716 Nmap ordinarily considers RST replies to be proof that the target
717 is up, this can lead to wasted time scanning targets that aren't
718 there. Using the --discovery-ignore-rst will prevent Nmap from
719 considering these replies during host discovery. You may need to
720 select extra host discovery options to ensure you don't miss
721 targets in this case.
722 --traceroute (Trace path to host)
724 Traceroutes are performed post-scan using information from the scan
725 results to determine the port and protocol most likely to reach the
726 target. It works with all scan types except connect scans (-sT) and
727 idle scans (-sI). All traces use Nmap's dynamic timing model and
728 are performed in parallel.
729 Traceroute works by sending packets with a low TTL (time-to-live)
731 in an attempt to elicit ICMP Time Exceeded messages from
732 intermediate hops between the scanner and the target host. Standard
733 traceroute implementations start with a TTL of 1 and increment the
734 TTL until the destination host is reached. Nmap's traceroute starts
735 with a high TTL and then decrements the TTL until it reaches zero.
736 Doing it backwards lets Nmap employ clever caching algorithms to
737 speed up traces over multiple hosts. On average Nmap sends 5–10
738 fewer packets per host, depending on network conditions. If a
739 single subnet is being scanned (i.e. 192.168.0.0/24) Nmap may only
740 have to send two packets to most hosts.
741
743 While Nmap has grown in functionality over the years, it began as an
744 efficient port scanner, and that remains its core function. The simple
745 command nmap target scans 1,000 TCP ports on the host target. While
746 many port scanners have traditionally lumped all ports into the open or
747 closed states, Nmap is much more granular. It divides ports into six
748 states: open, closed, filtered, unfiltered, open|filtered, or
749 closed|filtered.
750 These states are not intrinsic properties of the port itself, but
752 describe how Nmap sees them. For example, an Nmap scan from the same
753 network as the target may show port 135/tcp as open, while a scan at
754 the same time with the same options from across the Internet might show
755 that port as filtered.
756 The six port states recognized by Nmap
758 open
760 An application is actively accepting TCP connections, UDP datagrams
761 or SCTP associations on this port. Finding these is often the
762 primary goal of port scanning. Security-minded people know that
763 each open port is an avenue for attack. Attackers and pen-testers
764 want to exploit the open ports, while administrators try to close
765 or protect them with firewalls without thwarting legitimate users.
766 Open ports are also interesting for non-security scans because they
767 show services available for use on the network.
768 closed
770 A closed port is accessible (it receives and responds to Nmap probe
771 packets), but there is no application listening on it. They can be
772 helpful in showing that a host is up on an IP address (host
773 discovery, or ping scanning), and as part of OS detection. Because
774 closed ports are reachable, it may be worth scanning later in case
775 some open up. Administrators may want to consider blocking such
776 ports with a firewall. Then they would appear in the filtered
777 state, discussed next.
778 filtered
780 Nmap cannot determine whether the port is open because packet
781 filtering prevents its probes from reaching the port. The filtering
782 could be from a dedicated firewall device, router rules, or
783 host-based firewall software. These ports frustrate attackers
784 because they provide so little information. Sometimes they respond
785 with ICMP error messages such as type 3 code 13 (destination
786 unreachable: communication administratively prohibited), but
787 filters that simply drop probes without responding are far more
788 common. This forces Nmap to retry several times just in case the
789 probe was dropped due to network congestion rather than filtering.
790 This slows down the scan dramatically.
791 unfiltered
793 The unfiltered state means that a port is accessible, but Nmap is
794 unable to determine whether it is open or closed. Only the ACK
795 scan, which is used to map firewall rulesets, classifies ports into
796 this state. Scanning unfiltered ports with other scan types such as
797 Window scan, SYN scan, or FIN scan, may help resolve whether the
798 port is open.
799 open|filtered
801 Nmap places ports in this state when it is unable to determine
802 whether a port is open or filtered. This occurs for scan types in
803 which open ports give no response. The lack of response could also
804 mean that a packet filter dropped the probe or any response it
805 elicited. So Nmap does not know for sure whether the port is open
806 or being filtered. The UDP, IP protocol, FIN, NULL, and Xmas scans
807 classify ports this way.
808 closed|filtered
810 This state is used when Nmap is unable to determine whether a port
811 is closed or filtered. It is only used for the IP ID idle scan.
812
814 As a novice performing automotive repair, I can struggle for hours
815 trying to fit my rudimentary tools (hammer, duct tape, wrench, etc.) to
816 the task at hand. When I fail miserably and tow my jalopy to a real
817 mechanic, he invariably fishes around in a huge tool chest until
818 pulling out the perfect gizmo which makes the job seem effortless. The
819 art of port scanning is similar. Experts understand the dozens of scan
820 techniques and choose the appropriate one (or combination) for a given
821 task. Inexperienced users and script kiddies, on the other hand, try to
822 solve every problem with the default SYN scan. Since Nmap is free, the
823 only barrier to port scanning mastery is knowledge. That certainly
824 beats the automotive world, where it may take great skill to determine
825 that you need a strut spring compressor, then you still have to pay
826 thousands of dollars for it.
827 Most of the scan types are only available to privileged users. This is
829 because they send and receive raw packets, which requires root access
830 on Unix systems. Using an administrator account on Windows is
831 recommended, though Nmap sometimes works for unprivileged users on that
832 platform when Npcap has already been loaded into the OS. Requiring root
833 privileges was a serious limitation when Nmap was released in 1997, as
834 many users only had access to shared shell accounts. Now, the world is
835 different. Computers are cheaper, far more people have always-on direct
836 Internet access, and desktop Unix systems (including Linux and Mac OS
837 X) are prevalent. A Windows version of Nmap is now available, allowing
838 it to run on even more desktops. For all these reasons, users have less
839 need to run Nmap from limited shared shell accounts. This is fortunate,
840 as the privileged options make Nmap far more powerful and flexible.
841 While Nmap attempts to produce accurate results, keep in mind that all
843 of its insights are based on packets returned by the target machines
844 (or firewalls in front of them). Such hosts may be untrustworthy and
845 send responses intended to confuse or mislead Nmap. Much more common
846 are non-RFC-compliant hosts that do not respond as they should to Nmap
847 probes. FIN, NULL, and Xmas scans are particularly susceptible to this
848 problem. Such issues are specific to certain scan types and so are
849 discussed in the individual scan type entries.
850 This section documents the dozen or so port scan techniques supported
852 by Nmap. Only one method may be used at a time, except that UDP scan
853 (-sU) and any one of the SCTP scan types (-sY, -sZ) may be combined
854 with any one of the TCP scan types. As a memory aid, port scan type
855 options are of the form -sC, where C is a prominent character in the
856 scan name, usually the first. The one exception to this is the
857 deprecated FTP bounce scan (-b). By default, Nmap performs a SYN Scan,
858 though it substitutes a connect scan if the user does not have proper
859 privileges to send raw packets (requires root access on Unix). Of the
860 scans listed in this section, unprivileged users can only execute
861 connect and FTP bounce scans.
862 -sS (TCP SYN scan)
864 SYN scan is the default and most popular scan option for good
865 reasons. It can be performed quickly, scanning thousands of ports
866 per second on a fast network not hampered by restrictive firewalls.
867 It is also relatively unobtrusive and stealthy since it never
868 completes TCP connections. SYN scan works against any compliant TCP
869 stack rather than depending on idiosyncrasies of specific platforms
870 as Nmap's FIN/NULL/Xmas, Maimon and idle scans do. It also allows
871 clear, reliable differentiation between the open, closed, and
872 filtered states.
873 This technique is often referred to as half-open scanning, because
875 you don't open a full TCP connection. You send a SYN packet, as if
876 you are going to open a real connection and then wait for a
877 response. A SYN/ACK indicates the port is listening (open), while a
878 RST (reset) is indicative of a non-listener. If no response is
879 received after several retransmissions, the port is marked as
880 filtered. The port is also marked filtered if an ICMP unreachable
881 error (type 3, code 0, 1, 2, 3, 9, 10, or 13) is received. The port
882 is also considered open if a SYN packet (without the ACK flag) is
883 received in response. This can be due to an extremely rare TCP
884 feature known as a simultaneous open or split handshake connection
885 (see https://nmap.org/misc/split-handshake.pdf).
886 -sT (TCP connect scan)
888 TCP connect scan is the default TCP scan type when SYN scan is not
889 an option. This is the case when a user does not have raw packet
890 privileges. Instead of writing raw packets as most other scan types
891 do, Nmap asks the underlying operating system to establish a
892 connection with the target machine and port by issuing the connect
893 system call. This is the same high-level system call that web
894 browsers, P2P clients, and most other network-enabled applications
895 use to establish a connection. It is part of a programming
896 interface known as the Berkeley Sockets API. Rather than read raw
897 packet responses off the wire, Nmap uses this API to obtain status
898 information on each connection attempt.
899 When SYN scan is available, it is usually a better choice. Nmap has
901 less control over the high level connect call than with raw
902 packets, making it less efficient. The system call completes
903 connections to open target ports rather than performing the
904 half-open reset that SYN scan does. Not only does this take longer
905 and require more packets to obtain the same information, but target
906 machines are more likely to log the connection. A decent IDS will
907 catch either, but most machines have no such alarm system. Many
908 services on your average Unix system will add a note to syslog, and
909 sometimes a cryptic error message, when Nmap connects and then
910 closes the connection without sending data. Truly pathetic services
911 crash when this happens, though that is uncommon. An administrator
912 who sees a bunch of connection attempts in her logs from a single
913 system should know that she has been connect scanned.
914 -sU (UDP scans)
916 While most popular services on the Internet run over the TCP
917 protocol, UDP[5] services are widely deployed. DNS, SNMP, and DHCP
918 (registered ports 53, 161/162, and 67/68) are three of the most
919 common. Because UDP scanning is generally slower and more difficult
920 than TCP, some security auditors ignore these ports. This is a
921 mistake, as exploitable UDP services are quite common and attackers
922 certainly don't ignore the whole protocol. Fortunately, Nmap can
923 help inventory UDP ports.
924 UDP scan is activated with the -sU option. It can be combined with
926 a TCP scan type such as SYN scan (-sS) to check both protocols
927 during the same run.
928 UDP scan works by sending a UDP packet to every targeted port. For
930 some common ports such as 53 and 161, a protocol-specific payload
931 is sent to increase response rate, but for most ports the packet is
932 empty unless the --data, --data-string, or --data-length options
933 are specified. If an ICMP port unreachable error (type 3, code 3)
934 is returned, the port is closed. Other ICMP unreachable errors
935 (type 3, codes 0, 1, 2, 9, 10, or 13) mark the port as filtered.
936 Occasionally, a service will respond with a UDP packet, proving
937 that it is open. If no response is received after retransmissions,
938 the port is classified as open|filtered. This means that the port
939 could be open, or perhaps packet filters are blocking the
940 communication. Version detection (-sV) can be used to help
941 differentiate the truly open ports from the filtered ones.
942 A big challenge with UDP scanning is doing it quickly. Open and
944 filtered ports rarely send any response, leaving Nmap to time out
945 and then conduct retransmissions just in case the probe or response
946 were lost. Closed ports are often an even bigger problem. They
947 usually send back an ICMP port unreachable error. But unlike the
948 RST packets sent by closed TCP ports in response to a SYN or
949 connect scan, many hosts rate limit ICMP port unreachable messages
950 by default. Linux and Solaris are particularly strict about this.
951 For example, the Linux 2.4.20 kernel limits destination unreachable
952 messages to one per second (in net/ipv4/icmp.c).
953 Nmap detects rate limiting and slows down accordingly to avoid
955 flooding the network with useless packets that the target machine
956 will drop. Unfortunately, a Linux-style limit of one packet per
957 second makes a 65,536-port scan take more than 18 hours. Ideas for
958 speeding your UDP scans up include scanning more hosts in parallel,
959 doing a quick scan of just the popular ports first, scanning from
960 behind the firewall, and using --host-timeout to skip slow hosts.
961 -sY (SCTP INIT scan)
963 SCTP[6] is a relatively new alternative to the TCP and UDP
964 protocols, combining most characteristics of TCP and UDP, and also
965 adding new features like multi-homing and multi-streaming. It is
966 mostly being used for SS7/SIGTRAN related services but has the
967 potential to be used for other applications as well. SCTP INIT scan
968 is the SCTP equivalent of a TCP SYN scan. It can be performed
969 quickly, scanning thousands of ports per second on a fast network
970 not hampered by restrictive firewalls. Like SYN scan, INIT scan is
971 relatively unobtrusive and stealthy, since it never completes SCTP
972 associations. It also allows clear, reliable differentiation
973 between the open, closed, and filtered states.
974 This technique is often referred to as half-open scanning, because
976 you don't open a full SCTP association. You send an INIT chunk, as
977 if you are going to open a real association and then wait for a
978 response. An INIT-ACK chunk indicates the port is listening (open),
979 while an ABORT chunk is indicative of a non-listener. If no
980 response is received after several retransmissions, the port is
981 marked as filtered. The port is also marked filtered if an ICMP
982 unreachable error (type 3, code 0, 1, 2, 3, 9, 10, or 13) is
983 received.
984 -sN; -sF; -sX (TCP NULL, FIN, and Xmas scans)
986 These three scan types (even more are possible with the --scanflags
987 option described in the next section) exploit a subtle loophole in
988 the TCP RFC[7] to differentiate between open and closed ports. Page
989 65 of RFC 793 says that “if the [destination] port state is CLOSED
990 .... an incoming segment not containing a RST causes a RST to be
991 sent in response.” Then the next page discusses packets sent to
992 open ports without the SYN, RST, or ACK bits set, stating that:
993 “you are unlikely to get here, but if you do, drop the segment, and
994 return.”
995 When scanning systems compliant with this RFC text, any packet not
997 containing SYN, RST, or ACK bits will result in a returned RST if
998 the port is closed and no response at all if the port is open. As
999 long as none of those three bits are included, any combination of
1000 the other three (FIN, PSH, and URG) are OK. Nmap exploits this with
1001 three scan types:
1002 Null scan (-sN)
1004 Does not set any bits (TCP flag header is 0)
1005 FIN scan (-sF)
1007 Sets just the TCP FIN bit.
1008 Xmas scan (-sX)
1010 Sets the FIN, PSH, and URG flags, lighting the packet up like a
1011 Christmas tree.
1012 These three scan types are exactly the same in behavior except for
1014 the TCP flags set in probe packets. If a RST packet is received,
1015 the port is considered closed, while no response means it is
1016 open|filtered. The port is marked filtered if an ICMP unreachable
1017 error (type 3, code 0, 1, 2, 3, 9, 10, or 13) is received.
1018 The key advantage to these scan types is that they can sneak
1020 through certain non-stateful firewalls and packet filtering
1021 routers. Another advantage is that these scan types are a little
1022 more stealthy than even a SYN scan. Don't count on this though—most
1023 modern IDS products can be configured to detect them. The big
1024 downside is that not all systems follow RFC 793 to the letter. A
1025 number of systems send RST responses to the probes regardless of
1026 whether the port is open or not. This causes all of the ports to be
1027 labeled closed. Major operating systems that do this are Microsoft
1028 Windows, many Cisco devices, BSDI, and IBM OS/400. This scan does
1029 work against most Unix-based systems though. Another downside of
1030 these scans is that they can't distinguish open ports from certain
1031 filtered ones, leaving you with the response open|filtered.
1032 -sA (TCP ACK scan)
1034 This scan is different than the others discussed so far in that it
1035 never determines open (or even open|filtered) ports. It is used to
1036 map out firewall rulesets, determining whether they are stateful or
1037 not and which ports are filtered.
1038 The ACK scan probe packet has only the ACK flag set (unless you use
1040 --scanflags). When scanning unfiltered systems, open and closed
1041 ports will both return a RST packet. Nmap then labels them as
1042 unfiltered, meaning that they are reachable by the ACK packet, but
1043 whether they are open or closed is undetermined. Ports that don't
1044 respond, or send certain ICMP error messages back (type 3, code 0,
1045 1, 2, 3, 9, 10, or 13), are labeled filtered.
1046 -sW (TCP Window scan)
1048 Window scan is exactly the same as ACK scan except that it exploits
1049 an implementation detail of certain systems to differentiate open
1050 ports from closed ones, rather than always printing unfiltered when
1051 a RST is returned. It does this by examining the TCP Window field
1052 of the RST packets returned. On some systems, open ports use a
1053 positive window size (even for RST packets) while closed ones have
1054 a zero window. So instead of always listing a port as unfiltered
1055 when it receives a RST back, Window scan lists the port as open or
1056 closed if the TCP Window value in that reset is positive or zero,
1057 respectively.
1058 This scan relies on an implementation detail of a minority of
1060 systems out on the Internet, so you can't always trust it. Systems
1061 that don't support it will usually return all ports closed. Of
1062 course, it is possible that the machine really has no open ports.
1063 If most scanned ports are closed but a few common port numbers
1064 (such as 22, 25, 53) are filtered, the system is most likely
1065 susceptible. Occasionally, systems will even show the exact
1066 opposite behavior. If your scan shows 1,000 open ports and three
1067 closed or filtered ports, then those three may very well be the
1068 truly open ones.
1069 -sM (TCP Maimon scan)
1071 The Maimon scan is named after its discoverer, Uriel Maimon. He
1072 described the technique in Phrack Magazine issue #49 (November
1073 1996). Nmap, which included this technique, was released two
1074 issues later. This technique is exactly the same as NULL, FIN, and
1075 Xmas scans, except that the probe is FIN/ACK. According to RFC
1076 793[7] (TCP), a RST packet should be generated in response to such
1077 a probe whether the port is open or closed. However, Uriel noticed
1078 that many BSD-derived systems simply drop the packet if the port is
1079 open.
1080 --scanflags (Custom TCP scan)
1082 Truly advanced Nmap users need not limit themselves to the canned
1083 scan types offered. The --scanflags option allows you to design
1084 your own scan by specifying arbitrary TCP flags. Let your creative
1085 juices flow, while evading intrusion detection systems whose
1086 vendors simply paged through the Nmap man page adding specific
1087 rules!
1088 The --scanflags argument can be a numerical flag value such as 9
1090 (PSH and FIN), but using symbolic names is easier. Just mash
1091 together any combination of URG, ACK, PSH, RST, SYN, and FIN. For
1092 example, --scanflags URGACKPSHRSTSYNFIN sets everything, though
1093 it's not very useful for scanning. The order these are specified in
1094 is irrelevant.
1095 In addition to specifying the desired flags, you can specify a TCP
1097 scan type (such as -sA or -sF). That base type tells Nmap how to
1098 interpret responses. For example, a SYN scan considers no-response
1099 to indicate a filtered port, while a FIN scan treats the same as
1100 open|filtered. Nmap will behave the same way it does for the base
1101 scan type, except that it will use the TCP flags you specify
1102 instead. If you don't specify a base type, SYN scan is used.
1103 -sZ (SCTP COOKIE ECHO scan)
1105 SCTP COOKIE ECHO scan is a more advanced SCTP scan. It takes
1106 advantage of the fact that SCTP implementations should silently
1107 drop packets containing COOKIE ECHO chunks on open ports, but send
1108 an ABORT if the port is closed. The advantage of this scan type is
1109 that it is not as obvious a port scan than an INIT scan. Also,
1110 there may be non-stateful firewall rulesets blocking INIT chunks,
1111 but not COOKIE ECHO chunks. Don't be fooled into thinking that this
1112 will make a port scan invisible; a good IDS will be able to detect
1113 SCTP COOKIE ECHO scans too. The downside is that SCTP COOKIE ECHO
1114 scans cannot differentiate between open and filtered ports, leaving
1115 you with the state open|filtered in both cases.
1116 -sI zombie host[:probeport] (idle scan)
1118 This advanced scan method allows for a truly blind TCP port scan of
1119 the target (meaning no packets are sent to the target from your
1120 real IP address). Instead, a unique side-channel attack exploits
1121 predictable IP fragmentation ID sequence generation on the zombie
1122 host to glean information about the open ports on the target. IDS
1123 systems will display the scan as coming from the zombie machine you
1124 specify (which must be up and meet certain criteria). This
1125 fascinating scan type is too complex to fully describe in this
1126 reference guide, so I wrote and posted an informal paper with full
1127 details at https://nmap.org/book/idlescan.html.
1128 Besides being extraordinarily stealthy (due to its blind nature),
1130 this scan type permits mapping out IP-based trust relationships
1131 between machines. The port listing shows open ports from the
1132 perspective of the zombie host. So you can try scanning a target
1133 using various zombies that you think might be trusted (via
1134 router/packet filter rules).
1135 You can add a colon followed by a port number to the zombie host if
1137 you wish to probe a particular port on the zombie for IP ID
1138 changes. Otherwise Nmap will use the port it uses by default for
1139 TCP pings (80).
1140 -sO (IP protocol scan)
1142 IP protocol scan allows you to determine which IP protocols (TCP,
1143 ICMP, IGMP, etc.) are supported by target machines. This isn't
1144 technically a port scan, since it cycles through IP protocol
1145 numbers rather than TCP or UDP port numbers. Yet it still uses the
1146 -p option to select scanned protocol numbers, reports its results
1147 within the normal port table format, and even uses the same
1148 underlying scan engine as the true port scanning methods. So it is
1149 close enough to a port scan that it belongs here.
1150 Besides being useful in its own right, protocol scan demonstrates
1152 the power of open-source software. While the fundamental idea is
1153 pretty simple, I had not thought to add it nor received any
1154 requests for such functionality. Then in the summer of 2000,
1155 Gerhard Rieger conceived the idea, wrote an excellent patch
1156 implementing it, and sent it to the announce mailing list (then
1157 called nmap-hackers). I incorporated that patch into the Nmap tree
1158 and released a new version the next day. Few pieces of commercial
1159 software have users enthusiastic enough to design and contribute
1160 their own improvements!
1161 Protocol scan works in a similar fashion to UDP scan. Instead of
1163 iterating through the port number field of a UDP packet, it sends
1164 IP packet headers and iterates through the eight-bit IP protocol
1165 field. The headers are usually empty, containing no data and not
1166 even the proper header for the claimed protocol. The exceptions are
1167 TCP, UDP, ICMP, SCTP, and IGMP. A proper protocol header for those
1168 is included since some systems won't send them otherwise and
1169 because Nmap already has functions to create them. Instead of
1170 watching for ICMP port unreachable messages, protocol scan is on
1171 the lookout for ICMP protocol unreachable messages. If Nmap
1172 receives any response in any protocol from the target host, Nmap
1173 marks that protocol as open. An ICMP protocol unreachable error
1174 (type 3, code 2) causes the protocol to be marked as closed while
1175 port unreachable (type 3, code 3) marks the protocol open. Other
1176 ICMP unreachable errors (type 3, code 0, 1, 9, 10, or 13) cause the
1177 protocol to be marked filtered (though they prove that ICMP is open
1178 at the same time). If no response is received after
1179 retransmissions, the protocol is marked open|filtered
1180 -b FTP relay host (FTP bounce scan)
1182 An interesting feature of the FTP protocol (RFC 959[8]) is support
1183 for so-called proxy FTP connections. This allows a user to connect
1184 to one FTP server, then ask that files be sent to a third-party
1185 server. Such a feature is ripe for abuse on many levels, so most
1186 servers have ceased supporting it. One of the abuses this feature
1187 allows is causing the FTP server to port scan other hosts. Simply
1188 ask the FTP server to send a file to each interesting port of a
1189 target host in turn. The error message will describe whether the
1190 port is open or not. This is a good way to bypass firewalls because
1191 organizational FTP servers are often placed where they have more
1192 access to other internal hosts than any old Internet host would.
1193 Nmap supports FTP bounce scan with the -b option. It takes an
1194 argument of the form username:password@server:port. Server is the
1195 name or IP address of a vulnerable FTP server. As with a normal
1196 URL, you may omit username:password, in which case anonymous login
1197 credentials (user: anonymous password:-wwwuser@) are used. The port
1198 number (and preceding colon) may be omitted as well, in which case
1199 the default FTP port (21) on server is used.
1200 This vulnerability was widespread in 1997 when Nmap was released,
1202 but has largely been fixed. Vulnerable servers are still around, so
1203 it is worth trying when all else fails. If bypassing a firewall is
1204 your goal, scan the target network for port 21 (or even for any FTP
1205 services if you scan all ports with version detection) and use the
1206 ftp-bounce NSE script. Nmap will tell you whether the host is
1207 vulnerable or not. If you are just trying to cover your tracks, you
1208 don't need to (and, in fact, shouldn't) limit yourself to hosts on
1209 the target network. Before you go scanning random Internet
1210 addresses for vulnerable FTP servers, consider that sysadmins may
1211 not appreciate you abusing their servers in this way.
1212
1214 In addition to all of the scan methods discussed previously, Nmap
1215 offers options for specifying which ports are scanned and whether the
1216 scan order is randomized or sequential. By default, Nmap scans the most
1217 common 1,000 ports for each protocol.
1218 -p port ranges (Only scan specified ports)
1221 This option specifies which ports you want to scan and overrides
1222 the default. Individual port numbers are OK, as are ranges
1223 separated by a hyphen (e.g. 1-1023). The beginning and/or end
1224 values of a range may be omitted, causing Nmap to use 1 and 65535,
1225 respectively. So you can specify -p- to scan ports from 1 through
1226 65535. Scanning port zero is allowed if you specify it explicitly.
1227 For IP protocol scanning (-sO), this option specifies the protocol
1228 numbers you wish to scan for (0–255).
1229 When scanning a combination of protocols (e.g. TCP and UDP), you
1231 can specify a particular protocol by preceding the port numbers by
1232 T: for TCP, U: for UDP, S: for SCTP, or P: for IP Protocol. The
1233 qualifier lasts until you specify another qualifier. For example,
1234 the argument -p U:53,111,137,T:21-25,80,139,8080 would scan UDP
1235 ports 53, 111,and 137, as well as the listed TCP ports. Note that
1236 to scan both UDP and TCP, you have to specify -sU and at least one
1237 TCP scan type (such as -sS, -sF, or -sT). If no protocol qualifier
1238 is given, the port numbers are added to all protocol lists. Ports
1239 can also be specified by name according to what the port is
1240 referred to in the nmap-services. You can even use the wildcards *
1241 and ? with the names. For example, to scan FTP and all ports whose
1242 names begin with “http”, use -p ftp,http*. Be careful about shell
1243 expansions and quote the argument to -p if unsure.
1244 Ranges of ports can be surrounded by square brackets to indicate
1246 ports inside that range that appear in nmap-services. For example,
1247 the following will scan all ports in nmap-services equal to or
1248 below 1024: -p [-1024]. Be careful with shell expansions and quote
1249 the argument to -p if unsure.
1250 --exclude-ports port ranges (Exclude the specified ports from scanning)
1252 This option specifies which ports you do want Nmap to exclude from
1253 scanning. The port ranges are specified similar to -p. For IP
1254 protocol scanning (-sO), this option specifies the protocol numbers
1255 you wish to exclude (0–255).
1256 When ports are asked to be excluded, they are excluded from all
1258 types of scans (i.e. they will not be scanned under any
1259 circumstances). This also includes the discovery phase.
1260 -F (Fast (limited port) scan)
1262 Specifies that you wish to scan fewer ports than the default.
1263 Normally Nmap scans the most common 1,000 ports for each scanned
1264 protocol. With -F, this is reduced to 100.
1265 Nmap needs an nmap-services file with frequency information in
1267 order to know which ports are the most common. If port frequency
1268 information isn't available, perhaps because of the use of a custom
1269 nmap-services file, Nmap scans all named ports plus ports 1-1024.
1270 In that case, -F means to scan only ports that are named in the
1271 services file.
1272 -r (Don't randomize ports)
1274 By default, Nmap randomizes the scanned port order (except that
1275 certain commonly accessible ports are moved near the beginning for
1276 efficiency reasons). This randomization is normally desirable, but
1277 you can specify -r for sequential (sorted from lowest to highest)
1278 port scanning instead.
1279 --port-ratio ratio<decimal number between 0 and 1>
1281 Scans all ports in nmap-services file with a ratio greater than the
1282 one given. ratio must be between 0.0 and 1.0.
1283 --top-ports n
1285 Scans the n highest-ratio ports found in nmap-services file after
1286 excluding all ports specified by --exclude-ports. n must be 1 or
1287 greater.
1288
1290 Point Nmap at a remote machine and it might tell you that ports 25/tcp,
1291 80/tcp, and 53/udp are open. Using its nmap-services database of about
1292 2,200 well-known services, Nmap would report that those ports probably
1293 correspond to a mail server (SMTP), web server (HTTP), and name server
1294 (DNS) respectively. This lookup is usually accurate—the vast majority
1295 of daemons listening on TCP port 25 are, in fact, mail servers.
1296 However, you should not bet your security on this! People can and do
1297 run services on strange ports.
1298 Even if Nmap is right, and the hypothetical server above is running
1300 SMTP, HTTP, and DNS servers, that is not a lot of information. When
1301 doing vulnerability assessments (or even simple network inventories) of
1302 your companies or clients, you really want to know which mail and DNS
1303 servers and versions are running. Having an accurate version number
1304 helps dramatically in determining which exploits a server is vulnerable
1305 to. Version detection helps you obtain this information.
1306 After TCP and/or UDP ports are discovered using one of the other scan
1308 methods, version detection interrogates those ports to determine more
1309 about what is actually running. The nmap-service-probes database
1310 contains probes for querying various services and match expressions to
1311 recognize and parse responses. Nmap tries to determine the service
1312 protocol (e.g. FTP, SSH, Telnet, HTTP), the application name (e.g. ISC
1313 BIND, Apache httpd, Solaris telnetd), the version number, hostname,
1314 device type (e.g. printer, router), the OS family (e.g. Windows,
1315 Linux). When possible, Nmap also gets the Common Platform Enumeration
1316 (CPE) representation of this information. Sometimes miscellaneous
1317 details like whether an X server is open to connections, the SSH
1318 protocol version, or the KaZaA user name, are available. Of course,
1319 most services don't provide all of this information. If Nmap was
1320 compiled with OpenSSL support, it will connect to SSL servers to deduce
1321 the service listening behind that encryption layer. Some UDP ports are
1322 left in the open|filtered state after a UDP port scan is unable to
1323 determine whether the port is open or filtered. Version detection will
1324 try to elicit a response from these ports (just as it does with open
1325 ports), and change the state to open if it succeeds. open|filtered TCP
1326 ports are treated the same way. Note that the Nmap -A option enables
1327 version detection among other things. A paper documenting the
1328 workings, usage, and customization of version detection is available at
1329 https://nmap.org/book/vscan.html.
1330 When RPC services are discovered, the Nmap RPC grinder is automatically
1332 used to determine the RPC program and version numbers. It takes all the
1333 TCP/UDP ports detected as RPC and floods them with SunRPC program NULL
1334 commands in an attempt to determine whether they are RPC ports, and if
1335 so, what program and version number they serve up. Thus you can
1336 effectively obtain the same info as rpcinfo -p even if the target's
1337 portmapper is behind a firewall (or protected by TCP wrappers). Decoys
1338 do not currently work with RPC scan.
1339 When Nmap receives responses from a service but cannot match them to
1341 its database, it prints out a special fingerprint and a URL for you to
1342 submit it to if you know for sure what is running on the port. Please
1343 take a couple minutes to make the submission so that your find can
1344 benefit everyone. Thanks to these submissions, Nmap has about 6,500
1345 pattern matches for more than 650 protocols such as SMTP, FTP, HTTP,
1346 etc.
1347 Version detection is enabled and controlled with the following options:
1349 -sV (Version detection)
1351 Enables version detection, as discussed above. Alternatively, you
1352 can use -A, which enables version detection among other things.
1353 -sR is an alias for -sV. Prior to March 2011, it was used to active
1355 the RPC grinder separately from version detection, but now these
1356 options are always combined.
1357 --allports (Don't exclude any ports from version detection)
1359 By default, Nmap version detection skips TCP port 9100 because some
1360 printers simply print anything sent to that port, leading to dozens
1361 of pages of HTTP GET requests, binary SSL session requests, etc.
1362 This behavior can be changed by modifying or removing the Exclude
1363 directive in nmap-service-probes, or you can specify --allports to
1364 scan all ports regardless of any Exclude directive.
1365 --version-intensity intensity (Set version scan intensity)
1367 When performing a version scan (-sV), Nmap sends a series of
1368 probes, each of which is assigned a rarity value between one and
1369 nine. The lower-numbered probes are effective against a wide
1370 variety of common services, while the higher-numbered ones are
1371 rarely useful. The intensity level specifies which probes should be
1372 applied. The higher the number, the more likely it is the service
1373 will be correctly identified. However, high intensity scans take
1374 longer. The intensity must be between 0 and 9. The default is 7.
1375 When a probe is registered to the target port via the
1376 nmap-service-probes ports directive, that probe is tried regardless
1377 of intensity level. This ensures that the DNS probes will always be
1378 attempted against any open port 53, the SSL probe will be done
1379 against 443, etc.
1380 --version-light (Enable light mode)
1382 This is a convenience alias for --version-intensity 2. This light
1383 mode makes version scanning much faster, but it is slightly less
1384 likely to identify services.
1385 --version-all (Try every single probe)
1387 An alias for --version-intensity 9, ensuring that every single
1388 probe is attempted against each port.
1389 --version-trace (Trace version scan activity)
1391 This causes Nmap to print out extensive debugging info about what
1392 version scanning is doing. It is a subset of what you get with
1393 --packet-trace.
1394
1396 One of Nmap's best-known features is remote OS detection using TCP/IP
1397 stack fingerprinting. Nmap sends a series of TCP and UDP packets to the
1398 remote host and examines practically every bit in the responses. After
1399 performing dozens of tests such as TCP ISN sampling, TCP options
1400 support and ordering, IP ID sampling, and the initial window size
1401 check, Nmap compares the results to its nmap-os-db database of more
1402 than 2,600 known OS fingerprints and prints out the OS details if there
1403 is a match. Each fingerprint includes a freeform textual description of
1404 the OS, and a classification which provides the vendor name (e.g. Sun),
1405 underlying OS (e.g. Solaris), OS generation (e.g. 10), and device type
1406 (general purpose, router, switch, game console, etc). Most fingerprints
1407 also have a Common Platform Enumeration (CPE) representation, like
1408 cpe:/o:linux:linux_kernel:2.6.
1409 If Nmap is unable to guess the OS of a machine, and conditions are good
1411 (e.g. at least one open port and one closed port were found), Nmap will
1412 provide a URL you can use to submit the fingerprint if you know (for
1413 sure) the OS running on the machine. By doing this you contribute to
1414 the pool of operating systems known to Nmap and thus it will be more
1415 accurate for everyone.
1416 OS detection enables some other tests which make use of information
1418 that is gathered during the process anyway. One of these is TCP
1419 Sequence Predictability Classification. This measures approximately how
1420 hard it is to establish a forged TCP connection against the remote
1421 host. It is useful for exploiting source-IP based trust relationships
1422 (rlogin, firewall filters, etc) or for hiding the source of an attack.
1423 This sort of spoofing is rarely performed any more, but many machines
1424 are still vulnerable to it. The actual difficulty number is based on
1425 statistical sampling and may fluctuate. It is generally better to use
1426 the English classification such as “worthy challenge” or “trivial
1427 joke”. This is only reported in normal output in verbose (-v) mode.
1428 When verbose mode is enabled along with -O, IP ID sequence generation
1429 is also reported. Most machines are in the “incremental” class, which
1430 means that they increment the ID field in the IP header for each packet
1431 they send. This makes them vulnerable to several advanced information
1432 gathering and spoofing attacks.
1433 Another bit of extra information enabled by OS detection is a guess at
1435 a target's uptime. This uses the TCP timestamp option (RFC 1323[9]) to
1436 guess when a machine was last rebooted. The guess can be inaccurate due
1437 to the timestamp counter not being initialized to zero or the counter
1438 overflowing and wrapping around, so it is printed only in verbose mode.
1439 A paper documenting the workings, usage, and customization of OS
1441 detection is available at https://nmap.org/book/osdetect.html.
1442 OS detection is enabled and controlled with the following options:
1444 -O (Enable OS detection)
1446 Enables OS detection, as discussed above. Alternatively, you can
1447 use -A to enable OS detection along with other things.
1448 --osscan-limit (Limit OS detection to promising targets)
1450 OS detection is far more effective if at least one open and one
1451 closed TCP port are found. Set this option and Nmap will not even
1452 try OS detection against hosts that do not meet this criteria. This
1453 can save substantial time, particularly on -Pn scans against many
1454 hosts. It only matters when OS detection is requested with -O or
1455 -A.
1456 --osscan-guess; --fuzzy (Guess OS detection results)
1458 When Nmap is unable to detect a perfect OS match, it sometimes
1459 offers up near-matches as possibilities. The match has to be very
1460 close for Nmap to do this by default. Either of these (equivalent)
1461 options make Nmap guess more aggressively. Nmap will still tell you
1462 when an imperfect match is printed and display its confidence level
1463 (percentage) for each guess.
1464 --max-os-tries (Set the maximum number of OS detection tries against a
1466 target)
1467 When Nmap performs OS detection against a target and fails to find
1468 a perfect match, it usually repeats the attempt. By default, Nmap
1469 tries five times if conditions are favorable for OS fingerprint
1470 submission, and twice when conditions aren't so good. Specifying a
1471 lower --max-os-tries value (such as 1) speeds Nmap up, though you
1472 miss out on retries which could potentially identify the OS.
1473 Alternatively, a high value may be set to allow even more retries
1474 when conditions are favorable. This is rarely done, except to
1475 generate better fingerprints for submission and integration into
1476 the Nmap OS database.
1477
1479 The Nmap Scripting Engine (NSE) is one of Nmap's most powerful and
1480 flexible features. It allows users to write (and share) simple scripts
1481 (using the Lua programming language[10]
1482 ) to automate a wide variety of networking tasks. Those scripts are
1484 executed in parallel with the speed and efficiency you expect from
1485 Nmap. Users can rely on the growing and diverse set of scripts
1486 distributed with Nmap, or write their own to meet custom needs.
1487 Tasks we had in mind when creating the system include network
1489 discovery, more sophisticated version detection, vulnerability
1490 detection. NSE can even be used for vulnerability exploitation.
1491 To reflect those different uses and to simplify the choice of which
1493 scripts to run, each script contains a field associating it with one or
1494 more categories. Currently defined categories are auth, broadcast,
1495 default. discovery, dos, exploit, external, fuzzer, intrusive,
1496 malware, safe, version, and vuln. These are all described at
1497 https://nmap.org/book/nse-usage.html#nse-categories.
1498 Scripts are not run in a sandbox and thus could accidentally or
1500 maliciously damage your system or invade your privacy. Never run
1501 scripts from third parties unless you trust the authors or have
1502 carefully audited the scripts yourself.
1503 The Nmap Scripting Engine is described in detail at
1505 https://nmap.org/book/nse.html
1506 and is controlled by the following options:
1508 -sC
1510 Performs a script scan using the default set of scripts. It is
1511 equivalent to --script=default. Some of the scripts in this
1512 category are considered intrusive and should not be run against a
1513 target network without permission.
1514 --script filename|category|directory/|expression[,...]
1516 Runs a script scan using the comma-separated list of filenames,
1517 script categories, and directories. Each element in the list may
1518 also be a Boolean expression describing a more complex set of
1519 scripts. Each element is interpreted first as an expression, then
1520 as a category, and finally as a file or directory name.
1521 There are two special features for advanced users only. One is to
1523 prefix script names and expressions with + to force them to run
1524 even if they normally wouldn't (e.g. the relevant service wasn't
1525 detected on the target port). The other is that the argument all
1526 may be used to specify every script in Nmap's database. Be cautious
1527 with this because NSE contains dangerous scripts such as exploits,
1528 brute force authentication crackers, and denial of service attacks.
1529 File and directory names may be relative or absolute. Absolute
1531 names are used directly. Relative paths are looked for in the
1532 scripts of each of the following places until found:
1533 --datadir
1534 $NMAPDIR
1535 ~/.nmap (not searched on Windows)
1536 APPDATA\nmap (only on Windows)
1537 the directory containing the nmap executable
1538 the directory containing the nmap executable, followed by
1539 ../share/nmap (not searched on Windows)
1540 NMAPDATADIR (not searched on Windows)
1541 the current directory.
1542 When a directory name ending in / is given, Nmap loads every file
1544 in the directory whose name ends with .nse. All other files are
1545 ignored and directories are not searched recursively. When a
1546 filename is given, it does not have to have the .nse extension; it
1547 will be added automatically if necessary. Nmap scripts are stored
1548 in a scripts subdirectory of the Nmap data directory by default
1549 (see https://nmap.org/book/data-files.html).
1550 For efficiency, scripts are indexed in a database stored in
1552 scripts/script.db, which lists the category or categories in which
1553 each script belongs. When referring to scripts from script.db by
1554 name, you can use a shell-style ‘*’ wildcard.
1555 nmap --script "http-*"
1557 Loads all scripts whose name starts with http-, such as
1558 http-auth and http-open-proxy. The argument to --script had to
1559 be in quotes to protect the wildcard from the shell.
1560 More complicated script selection can be done using the and, or,
1562 and not operators to build Boolean expressions. The operators have
1563 the same precedence[11] as in Lua: not is the highest, followed by
1564 and and then or. You can alter precedence by using parentheses.
1565 Because expressions contain space characters it is necessary to
1566 quote them.
1567 nmap --script "not intrusive"
1569 Loads every script except for those in the intrusive category.
1570 nmap --script "default or safe"
1572 This is functionally equivalent to nmap --script
1573 "default,safe". It loads all scripts that are in the default
1574 category or the safe category or both.
1575 nmap --script "default and safe"
1577 Loads those scripts that are in both the default and safe
1578 categories.
1579 nmap --script "(default or safe or intrusive) and not http-*"
1581 Loads scripts in the default, safe, or intrusive categories,
1582 except for those whose names start with http-.
1583 --script-args n1=v1,n2={n3=v3},n4={v4,v5}
1585 Lets you provide arguments to NSE scripts. Arguments are a
1586 comma-separated list of name=value pairs. Names and values may be
1587 strings not containing whitespace or the characters ‘{’, ‘}’, ‘=’,
1588 or ‘,’. To include one of these characters in a string, enclose the
1589 string in single or double quotes. Within a quoted string, ‘\’
1590 escapes a quote. A backslash is only used to escape quotation marks
1591 in this special case; in all other cases a backslash is interpreted
1592 literally. Values may also be tables enclosed in {}, just as in
1593 Lua. A table may contain simple string values or more name-value
1594 pairs, including nested tables. Many scripts qualify their
1595 arguments with the script name, as in xmpp-info.server_name. You
1596 may use that full qualified version to affect just the specified
1597 script, or you may pass the unqualified version (server_name in
1598 this case) to affect all scripts using that argument name. A script
1599 will first check for its fully qualified argument name (the name
1600 specified in its documentation) before it accepts an unqualified
1601 argument name. A complex example of script arguments is
1602 --script-args
1603 'user=foo,pass=",{}=bar",whois={whodb=nofollow+ripe},xmpp-info.server_name=localhost'.
1604 The online NSE Documentation Portal at https://nmap.org/nsedoc/
1605 lists the arguments that each script accepts.
1606 --script-args-file filename
1608 Lets you load arguments to NSE scripts from a file. Any arguments
1609 on the command line supersede ones in the file. The file can be an
1610 absolute path, or a path relative to Nmap's usual search path
1611 (NMAPDIR, etc.) Arguments can be comma-separated or
1612 newline-separated, but otherwise follow the same rules as for
1613 --script-args, without requiring special quoting and escaping,
1614 since they are not parsed by the shell.
1615 --script-help filename|category|directory|expression|all[,...]
1617 Shows help about scripts. For each script matching the given
1618 specification, Nmap prints the script name, its categories, and its
1619 description. The specifications are the same as those accepted by
1620 --script; so for example if you want help about the ftp-anon
1621 script, you would run nmap --script-help ftp-anon. In addition to
1622 getting help for individual scripts, you can use this as a preview
1623 of what scripts will be run for a specification, for example with
1624 nmap --script-help default.
1625 --script-trace
1627 This option does what --packet-trace does, just one ISO layer
1628 higher. If this option is specified all incoming and outgoing
1629 communication performed by a script is printed. The displayed
1630 information includes the communication protocol, the source, the
1631 target and the transmitted data. If more than 5% of all transmitted
1632 data is not printable, then the trace output is in a hex dump
1633 format. Specifying --packet-trace enables script tracing too.
1634 --script-updatedb
1636 This option updates the script database found in scripts/script.db
1637 which is used by Nmap to determine the available default scripts
1638 and categories. It is only necessary to update the database if you
1639 have added or removed NSE scripts from the default scripts
1640 directory or if you have changed the categories of any script. This
1641 option is generally used by itself: nmap --script-updatedb.
1642
1644 One of my highest Nmap development priorities has always been
1645 performance. A default scan (nmap hostname) of a host on my local
1646 network takes a fifth of a second. That is barely enough time to blink,
1647 but adds up when you are scanning hundreds or thousands of hosts.
1648 Moreover, certain scan options such as UDP scanning and version
1649 detection can increase scan times substantially. So can certain
1650 firewall configurations, particularly response rate limiting. While
1651 Nmap utilizes parallelism and many advanced algorithms to accelerate
1652 these scans, the user has ultimate control over how Nmap runs. Expert
1653 users carefully craft Nmap commands to obtain only the information they
1654 care about while meeting their time constraints.
1655 Techniques for improving scan times include omitting non-critical
1657 tests, and upgrading to the latest version of Nmap (performance
1658 enhancements are made frequently). Optimizing timing parameters can
1659 also make a substantial difference. Those options are listed below.
1660 Some options accept a time parameter. This is specified in seconds by
1662 default, though you can append ‘ms’, ‘s’, ‘m’, or ‘h’ to the value to
1663 specify milliseconds, seconds, minutes, or hours. So the --host-timeout
1664 arguments 900000ms, 900, 900s, and 15m all do the same thing.
1665 --min-hostgroup numhosts; --max-hostgroup numhosts (Adjust parallel
1667 scan group sizes)
1668 Nmap has the ability to port scan or version scan multiple hosts in
1669 parallel. Nmap does this by dividing the target IP space into
1670 groups and then scanning one group at a time. In general, larger
1671 groups are more efficient. The downside is that host results can't
1672 be provided until the whole group is finished. So if Nmap started
1673 out with a group size of 50, the user would not receive any reports
1674 (except for the updates offered in verbose mode) until the first 50
1675 hosts are completed.
1676 By default, Nmap takes a compromise approach to this conflict. It
1678 starts out with a group size as low as five so the first results
1679 come quickly and then increases the groupsize to as high as 1024.
1680 The exact default numbers depend on the options given. For
1681 efficiency reasons, Nmap uses larger group sizes for UDP or
1682 few-port TCP scans.
1683 When a maximum group size is specified with --max-hostgroup, Nmap
1685 will never exceed that size. Specify a minimum size with
1686 --min-hostgroup and Nmap will try to keep group sizes above that
1687 level. Nmap may have to use smaller groups than you specify if
1688 there are not enough target hosts left on a given interface to
1689 fulfill the specified minimum. Both may be set to keep the group
1690 size within a specific range, though this is rarely desired.
1691 These options do not have an effect during the host discovery phase
1693 of a scan. This includes plain ping scans (-sn). Host discovery
1694 always works in large groups of hosts to improve speed and
1695 accuracy.
1696 The primary use of these options is to specify a large minimum
1698 group size so that the full scan runs more quickly. A common choice
1699 is 256 to scan a network in /24 sized chunks. For a scan with many
1700 ports, exceeding that number is unlikely to help much. For scans of
1701 just a few port numbers, host group sizes of 2048 or more may be
1702 helpful.
1703 --min-parallelism numprobes; --max-parallelism numprobes (Adjust probe
1705 parallelization)
1706 These options control the total number of probes that may be
1707 outstanding for a host group. They are used for port scanning and
1708 host discovery. By default, Nmap calculates an ever-changing ideal
1709 parallelism based on network performance. If packets are being
1710 dropped, Nmap slows down and allows fewer outstanding probes. The
1711 ideal probe number slowly rises as the network proves itself
1712 worthy. These options place minimum or maximum bounds on that
1713 variable. By default, the ideal parallelism can drop to one if the
1714 network proves unreliable and rise to several hundred in perfect
1715 conditions.
1716 The most common usage is to set --min-parallelism to a number
1718 higher than one to speed up scans of poorly performing hosts or
1719 networks. This is a risky option to play with, as setting it too
1720 high may affect accuracy. Setting this also reduces Nmap's ability
1721 to control parallelism dynamically based on network conditions. A
1722 value of 10 might be reasonable, though I only adjust this value as
1723 a last resort.
1724 The --max-parallelism option is sometimes set to one to prevent
1726 Nmap from sending more than one probe at a time to hosts. The
1727 --scan-delay option, discussed later, is another way to do this.
1728 --min-rtt-timeout time, --max-rtt-timeout time, --initial-rtt-timeout
1730 time (Adjust probe timeouts)
1731 Nmap maintains a running timeout value for determining how long it
1732 will wait for a probe response before giving up or retransmitting
1733 the probe. This is calculated based on the response times of
1734 previous probes.
1735 If the network latency shows itself to be significant and variable,
1737 this timeout can grow to several seconds. It also starts at a
1738 conservative (high) level and may stay that way for a while when
1739 Nmap scans unresponsive hosts.
1740 Specifying a lower --max-rtt-timeout and --initial-rtt-timeout than
1742 the defaults can cut scan times significantly. This is particularly
1743 true for pingless (-Pn) scans, and those against heavily filtered
1744 networks. Don't get too aggressive though. The scan can end up
1745 taking longer if you specify such a low value that many probes are
1746 timing out and retransmitting while the response is in transit.
1747 If all the hosts are on a local network, 100 milliseconds
1749 (--max-rtt-timeout 100ms) is a reasonable aggressive value. If
1750 routing is involved, ping a host on the network first with the ICMP
1751 ping utility, or with a custom packet crafter such as Nping that is
1752 more likely to get through a firewall. Look at the maximum round
1753 trip time out of ten packets or so. You might want to double that
1754 for the --initial-rtt-timeout and triple or quadruple it for the
1755 --max-rtt-timeout. I generally do not set the maximum RTT below
1756 100 ms, no matter what the ping times are. Nor do I exceed 1000 ms.
1757 --min-rtt-timeout is a rarely used option that could be useful when
1759 a network is so unreliable that even Nmap's default is too
1760 aggressive. Since Nmap only reduces the timeout down to the minimum
1761 when the network seems to be reliable, this need is unusual and
1762 should be reported as a bug to the nmap-dev mailing list.
1763 --max-retries numtries (Specify the maximum number of port scan probe
1765 retransmissions)
1766 When Nmap receives no response to a port scan probe, it could mean
1767 the port is filtered. Or maybe the probe or response was simply
1768 lost on the network. It is also possible that the target host has
1769 rate limiting enabled that temporarily blocked the response. So
1770 Nmap tries again by retransmitting the initial probe. If Nmap
1771 detects poor network reliability, it may try many more times before
1772 giving up on a port. While this benefits accuracy, it also
1773 lengthens scan times. When performance is critical, scans may be
1774 sped up by limiting the number of retransmissions allowed. You can
1775 even specify --max-retries 0 to prevent any retransmissions, though
1776 that is only recommended for situations such as informal surveys
1777 where occasional missed ports and hosts are acceptable.
1778 The default (with no -T template) is to allow ten retransmissions.
1780 If a network seems reliable and the target hosts aren't rate
1781 limiting, Nmap usually only does one retransmission. So most target
1782 scans aren't even affected by dropping --max-retries to a low value
1783 such as three. Such values can substantially speed scans of slow
1784 (rate limited) hosts. You usually lose some information when Nmap
1785 gives up on ports early, though that may be preferable to letting
1786 the --host-timeout expire and losing all information about the
1787 target.
1788 --host-timeout time (Give up on slow target hosts)
1790 Some hosts simply take a long time to scan. This may be due to
1791 poorly performing or unreliable networking hardware or software,
1792 packet rate limiting, or a restrictive firewall. The slowest few
1793 percent of the scanned hosts can eat up a majority of the scan
1794 time. Sometimes it is best to cut your losses and skip those hosts
1795 initially. Specify --host-timeout with the maximum amount of time
1796 you are willing to wait. For example, specify 30m to ensure that
1797 Nmap doesn't waste more than half an hour on a single host. Note
1798 that Nmap may be scanning other hosts at the same time during that
1799 half an hour, so it isn't a complete loss. A host that times out is
1800 skipped. No port table, OS detection, or version detection results
1801 are printed for that host.
1802 The special value 0 can be used to mean “no timeout”, which can be
1804 used to override the T5 timing template, which sets the host
1805 timeout to 15 minutes.
1806 --script-timeout time
1808 While some scripts complete in fractions of a second, others can
1809 take hours or more depending on the nature of the script, arguments
1810 passed in, network and application conditions, and more. The
1811 --script-timeout option sets a ceiling on script execution time.
1812 Any script instance which exceeds that time will be terminated and
1813 no output will be shown. If debugging (-d) is enabled, Nmap will
1814 report on each timeout. For host and service scripts, a script
1815 instance only scans a single target host or port and the timeout
1816 period will be reset for the next instance.
1817 The special value 0 can be used to mean “no timeout”, which can be
1819 used to override the T5 timing template, which sets the script
1820 timeout to 10 minutes.
1821 --scan-delay time; --max-scan-delay time (Adjust delay between probes)
1823 This option causes Nmap to wait at least the given amount of time
1824 between each probe it sends to a given host. This is particularly
1825 useful in the case of rate limiting. Solaris machines (among many
1826 others) will usually respond to UDP scan probe packets with only
1827 one ICMP message per second. Any more than that sent by Nmap will
1828 be wasteful. A --scan-delay of 1s will keep Nmap at that slow rate.
1829 Nmap tries to detect rate limiting and adjust the scan delay
1830 accordingly, but it doesn't hurt to specify it explicitly if you
1831 already know what rate works best.
1832 When Nmap adjusts the scan delay upward to cope with rate limiting,
1834 the scan slows down dramatically. The --max-scan-delay option
1835 specifies the largest delay that Nmap will allow. A low
1836 --max-scan-delay can speed up Nmap, but it is risky. Setting this
1837 value too low can lead to wasteful packet retransmissions and
1838 possible missed ports when the target implements strict rate
1839 limiting.
1840 Another use of --scan-delay is to evade threshold based intrusion
1842 detection and prevention systems (IDS/IPS).
1843 --min-rate number; --max-rate number (Directly control the scanning
1845 rate)
1846 Nmap's dynamic timing does a good job of finding an appropriate
1847 speed at which to scan. Sometimes, however, you may happen to know
1848 an appropriate scanning rate for a network, or you may have to
1849 guarantee that a scan will be finished by a certain time. Or
1850 perhaps you must keep Nmap from scanning too quickly. The
1851 --min-rate and --max-rate options are designed for these
1852 situations.
1853 When the --min-rate option is given Nmap will do its best to send
1855 packets as fast as or faster than the given rate. The argument is a
1856 positive real number representing a packet rate in packets per
1857 second. For example, specifying --min-rate 300 means that Nmap will
1858 try to keep the sending rate at or above 300 packets per second.
1859 Specifying a minimum rate does not keep Nmap from going faster if
1860 conditions warrant.
1861 Likewise, --max-rate limits a scan's sending rate to a given
1863 maximum. Use --max-rate 100, for example, to limit sending to 100
1864 packets per second on a fast network. Use --max-rate 0.1 for a slow
1865 scan of one packet every ten seconds. Use --min-rate and --max-rate
1866 together to keep the rate inside a certain range.
1867 These two options are global, affecting an entire scan, not
1869 individual hosts. They only affect port scans and host discovery
1870 scans. Other features like OS detection implement their own timing.
1871 There are two conditions when the actual scanning rate may fall
1873 below the requested minimum. The first is if the minimum is faster
1874 than the fastest rate at which Nmap can send, which is dependent on
1875 hardware. In this case Nmap will simply send packets as fast as
1876 possible, but be aware that such high rates are likely to cause a
1877 loss of accuracy. The second case is when Nmap has nothing to send,
1878 for example at the end of a scan when the last probes have been
1879 sent and Nmap is waiting for them to time out or be responded to.
1880 It's normal to see the scanning rate drop at the end of a scan or
1881 in between hostgroups. The sending rate may temporarily exceed the
1882 maximum to make up for unpredictable delays, but on average the
1883 rate will stay at or below the maximum.
1884 Specifying a minimum rate should be done with care. Scanning faster
1886 than a network can support may lead to a loss of accuracy. In some
1887 cases, using a faster rate can make a scan take longer than it
1888 would with a slower rate. This is because Nmap's adaptive
1889 retransmission algorithms will detect the network congestion caused
1890 by an excessive scanning rate and increase the number of
1891 retransmissions in order to improve accuracy. So even though
1892 packets are sent at a higher rate, more packets are sent overall.
1893 Cap the number of retransmissions with the --max-retries option if
1894 you need to set an upper limit on total scan time.
1895 --defeat-rst-ratelimit
1897 Many hosts have long used rate limiting to reduce the number of
1898 ICMP error messages (such as port-unreachable errors) they send.
1899 Some systems now apply similar rate limits to the RST (reset)
1900 packets they generate. This can slow Nmap down dramatically as it
1901 adjusts its timing to reflect those rate limits. You can tell Nmap
1902 to ignore those rate limits (for port scans such as SYN scan which
1903 don't treat non-responsive ports as open) by specifying
1904 --defeat-rst-ratelimit.
1905 Using this option can reduce accuracy, as some ports will appear
1907 non-responsive because Nmap didn't wait long enough for a
1908 rate-limited RST response. With a SYN scan, the non-response
1909 results in the port being labeled filtered rather than the closed
1910 state we see when RST packets are received. This option is useful
1911 when you only care about open ports, and distinguishing between
1912 closed and filtered ports isn't worth the extra time.
1913 --defeat-icmp-ratelimit
1915 Similar to --defeat-rst-ratelimit, the --defeat-icmp-ratelimit
1916 option trades accuracy for speed, increasing UDP scanning speed
1917 against hosts that rate-limit ICMP error messages. Because this
1918 option causes Nmap to not delay in order to receive the port
1919 unreachable messages, a non-responsive port will be labeled
1920 closed|filtered instead of the default open|filtered. This has the
1921 effect of only treating ports which actually respond via UDP as
1922 open. Since many UDP services do not respond in this way, the
1923 chance for inaccuracy is greater with this option than with
1924 --defeat-rst-ratelimit.
1925 --nsock-engine iocp|epoll|kqueue|poll|select
1927 Enforce use of a given nsock IO multiplexing engine. Only the
1928 select(2)-based fallback engine is guaranteed to be available on
1929 your system. Engines are named after the name of the IO management
1930 facility they leverage. Engines currently implemented are epoll,
1931 kqueue, poll, and select, but not all will be present on any
1932 platform. By default, Nmap will use the "best" engine, i.e. the
1933 first one in this list that is supported. Use nmap -V to see which
1934 engines are supported on your platform.
1935 -T paranoid|sneaky|polite|normal|aggressive|insane (Set a timing
1937 template)
1938 While the fine-grained timing controls discussed in the previous
1939 section are powerful and effective, some people find them
1940 confusing. Moreover, choosing the appropriate values can sometimes
1941 take more time than the scan you are trying to optimize.
1942 Fortunately, Nmap offers a simpler approach, with six timing
1943 templates. You can specify them with the -T option and their number
1944 (0–5) or their name. The template names are paranoid (0),
1945 sneaky (1), polite (2), normal (3), aggressive (4), and insane (5).
1946 The first two are for IDS evasion. Polite mode slows down the scan
1947 to use less bandwidth and target machine resources. Normal mode is
1948 the default and so -T3 does nothing. Aggressive mode speeds scans
1949 up by making the assumption that you are on a reasonably fast and
1950 reliable network. Finally insane mode assumes that you are on an
1951 extraordinarily fast network or are willing to sacrifice some
1952 accuracy for speed.
1953 These templates allow the user to specify how aggressive they wish
1955 to be, while leaving Nmap to pick the exact timing values. The
1956 templates also make some minor speed adjustments for which
1957 fine-grained control options do not currently exist. For example,
1958 -T4 prohibits the dynamic scan delay from exceeding 10 ms for TCP
1959 ports and -T5 caps that value at 5 ms. Templates can be used in
1960 combination with fine-grained controls, and the fine-grained
1961 controls that you specify will take precedence over the timing
1962 template default for that parameter. I recommend using -T4 when
1963 scanning reasonably modern and reliable networks. Keep that option
1964 even when you add fine-grained controls so that you benefit from
1965 those extra minor optimizations that it enables.
1966 If you are on a decent broadband or ethernet connection, I would
1968 recommend always using -T4. Some people love -T5 though it is too
1969 aggressive for my taste. People sometimes specify -T2 because they
1970 think it is less likely to crash hosts or because they consider
1971 themselves to be polite in general. They often don't realize just
1972 how slow -T polite really is. Their scan may take ten times longer
1973 than a default scan. Machine crashes and bandwidth problems are
1974 rare with the default timing options (-T3) and so I normally
1975 recommend that for cautious scanners. Omitting version detection is
1976 far more effective than playing with timing values at reducing
1977 these problems.
1978 While -T0 and -T1 may be useful for avoiding IDS alerts, they will
1980 take an extraordinarily long time to scan thousands of machines or
1981 ports. For such a long scan, you may prefer to set the exact timing
1982 values you need rather than rely on the canned -T0 and -T1 values.
1983 The main effects of T0 are serializing the scan so only one port is
1985 scanned at a time, and waiting five minutes between sending each
1986 probe. T1 and T2 are similar but they only wait 15 seconds and 0.4
1987 seconds, respectively, between probes. T3 is Nmap's default
1988 behavior, which includes parallelization. -T4 does the equivalent
1989 of --max-rtt-timeout 1250ms --min-rtt-timeout 100ms
1990 --initial-rtt-timeout 500ms --max-retries 6 and sets the maximum
1991 TCP and SCTP scan delay to 10ms. T5 does the equivalent of
1992 --max-rtt-timeout 300ms --min-rtt-timeout 50ms
1993 --initial-rtt-timeout 250ms --max-retries 2 --host-timeout 15m
1994 --script-timeout 10m --max-scan-delay as well as setting the
1995 maximum TCP and SCTP scan delay to 5ms. Maximum UDP scan delay is
1996 not set by T4 or T5, but it can be set with the --max-scan-delay
1997 option.
1998
2000 Many Internet pioneers envisioned a global open network with a
2001 universal IP address space allowing virtual connections between any two
2002 nodes. This allows hosts to act as true peers, serving and retrieving
2003 information from each other. People could access all of their home
2004 systems from work, changing the climate control settings or unlocking
2005 the doors for early guests. This vision of universal connectivity has
2006 been stifled by address space shortages and security concerns. In the
2007 early 1990s, organizations began deploying firewalls for the express
2008 purpose of reducing connectivity. Huge networks were cordoned off from
2009 the unfiltered Internet by application proxies, network address
2010 translation, and packet filters. The unrestricted flow of information
2011 gave way to tight regulation of approved communication channels and the
2012 content that passes over them.
2013 Network obstructions such as firewalls can make mapping a network
2015 exceedingly difficult. It will not get any easier, as stifling casual
2016 reconnaissance is often a key goal of implementing the devices.
2017 Nevertheless, Nmap offers many features to help understand these
2018 complex networks, and to verify that filters are working as intended.
2019 It even supports mechanisms for bypassing poorly implemented defenses.
2020 One of the best methods of understanding your network security posture
2021 is to try to defeat it. Place yourself in the mind-set of an attacker,
2022 and deploy techniques from this section against your networks. Launch
2023 an FTP bounce scan, idle scan, fragmentation attack, or try to tunnel
2024 through one of your own proxies.
2025 In addition to restricting network activity, companies are increasingly
2027 monitoring traffic with intrusion detection systems (IDS). All of the
2028 major IDSs ship with rules designed to detect Nmap scans because scans
2029 are sometimes a precursor to attacks. Many of these products have
2030 recently morphed into intrusion prevention systems (IPS) that actively
2031 block traffic deemed malicious. Unfortunately for network
2032 administrators and IDS vendors, reliably detecting bad intentions by
2033 analyzing packet data is a tough problem. Attackers with patience,
2034 skill, and the help of certain Nmap options can usually pass by IDSs
2035 undetected. Meanwhile, administrators must cope with large numbers of
2036 false positive results where innocent activity is misdiagnosed and
2037 alerted on or blocked.
2038 Occasionally people suggest that Nmap should not offer features for
2040 evading firewall rules or sneaking past IDSs. They argue that these
2041 features are just as likely to be misused by attackers as used by
2042 administrators to enhance security. The problem with this logic is that
2043 these methods would still be used by attackers, who would just find
2044 other tools or patch the functionality into Nmap. Meanwhile,
2045 administrators would find it that much harder to do their jobs.
2046 Deploying only modern, patched FTP servers is a far more powerful
2047 defense than trying to prevent the distribution of tools implementing
2048 the FTP bounce attack.
2049 There is no magic bullet (or Nmap option) for detecting and subverting
2051 firewalls and IDS systems. It takes skill and experience. A tutorial is
2052 beyond the scope of this reference guide, which only lists the relevant
2053 options and describes what they do.
2054 -f (fragment packets); --mtu (using the specified MTU)
2056 The -f option causes the requested scan (including host discovery
2057 scans) to use tiny fragmented IP packets. The idea is to split up
2058 the TCP header over several packets to make it harder for packet
2059 filters, intrusion detection systems, and other annoyances to
2060 detect what you are doing. Be careful with this! Some programs have
2061 trouble handling these tiny packets. The old-school sniffer named
2062 Sniffit segmentation faulted immediately upon receiving the first
2063 fragment. Specify this option once, and Nmap splits the packets
2064 into eight bytes or less after the IP header. So a 20-byte TCP
2065 header would be split into three packets. Two with eight bytes of
2066 the TCP header, and one with the final four. Of course each
2067 fragment also has an IP header. Specify -f again to use 16 bytes
2068 per fragment (reducing the number of fragments). Or you can
2069 specify your own offset size with the --mtu option. Don't also
2070 specify -f if you use --mtu. The offset must be a multiple of
2071 eight. While fragmented packets won't get by packet filters and
2072 firewalls that queue all IP fragments, such as the
2073 CONFIG_IP_ALWAYS_DEFRAG option in the Linux kernel, some networks
2074 can't afford the performance hit this causes and thus leave it
2075 disabled. Others can't enable this because fragments may take
2076 different routes into their networks. Some source systems
2077 defragment outgoing packets in the kernel. Linux with the iptables
2078 connection tracking module is one such example. Do a scan while a
2079 sniffer such as Wireshark is running to ensure that sent packets
2080 are fragmented. If your host OS is causing problems, try the
2081 --send-eth option to bypass the IP layer and send raw ethernet
2082 frames.
2083 Fragmentation is only supported for Nmap's raw packet features,
2085 which includes TCP and UDP port scans (except connect scan and FTP
2086 bounce scan) and OS detection. Features such as version detection
2087 and the Nmap Scripting Engine generally don't support fragmentation
2088 because they rely on your host's TCP stack to communicate with
2089 target services.
2090 -D decoy1[,decoy2][,ME][,...] (Cloak a scan with decoys)
2092 Causes a decoy scan to be performed, which makes it appear to the
2093 remote host that the host(s) you specify as decoys are scanning the
2094 target network too. Thus their IDS might report 5–10 port scans
2095 from unique IP addresses, but they won't know which IP was scanning
2096 them and which were innocent decoys. While this can be defeated
2097 through router path tracing, response-dropping, and other active
2098 mechanisms, it is generally an effective technique for hiding your
2099 IP address.
2100 Separate each decoy host with commas, and you can optionally use ME
2102 as one of the decoys to represent the position for your real IP
2103 address. If you put ME in the sixth position or later, some common
2104 port scan detectors (such as Solar Designer's excellent Scanlogd)
2105 are unlikely to show your IP address at all. If you don't use ME,
2106 Nmap will put you in a random position. You can also use RND to
2107 generate a random, non-reserved IP address, or RND:number to
2108 generate number addresses.
2109 Note that the hosts you use as decoys should be up or you might
2111 accidentally SYN flood your targets. Also it will be pretty easy to
2112 determine which host is scanning if only one is actually up on the
2113 network. You might want to use IP addresses instead of names (so
2114 the decoy networks don't see you in their nameserver logs). Right
2115 now random IP address generation is only supported with IPv4
2116 Decoys are used both in the initial host discovery scan (using
2118 ICMP, SYN, ACK, or whatever) and during the actual port scanning
2119 phase. Decoys are also used during remote OS detection (-O). Decoys
2120 do not work with version detection or TCP connect scan. When a scan
2121 delay is in effect, the delay is enforced between each batch of
2122 spoofed probes, not between each individual probe. Because decoys
2123 are sent as a batch all at once, they may temporarily violate
2124 congestion control limits.
2125 It is worth noting that using too many decoys may slow your scan
2127 and potentially even make it less accurate. Also, some ISPs will
2128 filter out your spoofed packets, but many do not restrict spoofed
2129 IP packets at all.
2130 -S IP_Address (Spoof source address)
2132 In some circumstances, Nmap may not be able to determine your
2133 source address (Nmap will tell you if this is the case). In this
2134 situation, use -S with the IP address of the interface you wish to
2135 send packets through.
2136 Another possible use of this flag is to spoof the scan to make the
2138 targets think that someone else is scanning them. Imagine a company
2139 being repeatedly port scanned by a competitor! The -e option and
2140 -Pn are generally required for this sort of usage. Note that you
2141 usually won't receive reply packets back (they will be addressed to
2142 the IP you are spoofing), so Nmap won't produce useful reports.
2143 -e interface (Use specified interface)
2145 Tells Nmap what interface to send and receive packets on. Nmap
2146 should be able to detect this automatically, but it will tell you
2147 if it cannot.
2148 --source-port portnumber; -g portnumber (Spoof source port number)
2150 One surprisingly common misconfiguration is to trust traffic based
2151 only on the source port number. It is easy to understand how this
2152 comes about. An administrator will set up a shiny new firewall,
2153 only to be flooded with complaints from ungrateful users whose
2154 applications stopped working. In particular, DNS may be broken
2155 because the UDP DNS replies from external servers can no longer
2156 enter the network. FTP is another common example. In active FTP
2157 transfers, the remote server tries to establish a connection back
2158 to the client to transfer the requested file.
2159 Secure solutions to these problems exist, often in the form of
2161 application-level proxies or protocol-parsing firewall modules.
2162 Unfortunately there are also easier, insecure solutions. Noting
2163 that DNS replies come from port 53 and active FTP from port 20,
2164 many administrators have fallen into the trap of simply allowing
2165 incoming traffic from those ports. They often assume that no
2166 attacker would notice and exploit such firewall holes. In other
2167 cases, administrators consider this a short-term stop-gap measure
2168 until they can implement a more secure solution. Then they forget
2169 the security upgrade.
2170 Overworked network administrators are not the only ones to fall
2172 into this trap. Numerous products have shipped with these insecure
2173 rules. Even Microsoft has been guilty. The IPsec filters that
2174 shipped with Windows 2000 and Windows XP contain an implicit rule
2175 that allows all TCP or UDP traffic from port 88 (Kerberos). In
2176 another well-known case, versions of the Zone Alarm personal
2177 firewall up to 2.1.25 allowed any incoming UDP packets with the
2178 source port 53 (DNS) or 67 (DHCP).
2179 Nmap offers the -g and --source-port options (they are equivalent)
2181 to exploit these weaknesses. Simply provide a port number and Nmap
2182 will send packets from that port where possible. Most scanning
2183 operations that use raw sockets, including SYN and UDP scans,
2184 support the option completely. The option notably doesn't have an
2185 effect for any operations that use normal operating system sockets,
2186 including DNS requests, TCP connect scan, version detection, and
2187 script scanning. Setting the source port also doesn't work for OS
2188 detection, because Nmap must use different port numbers for certain
2189 OS detection tests to work properly.
2190 --data hex string (Append custom binary data to sent packets)
2192 This option lets you include binary data as payload in sent
2193 packets. hex string may be specified in any of the following
2194 formats: 0xAABBCCDDEEFF..., AABBCCDDEEFF... or
2195 \xAA\xBB\xCC\xDD\xEE\xFF.... Examples of use are --data 0xdeadbeef
2196 and --data \xCA\xFE\x09. Note that if you specify a number like
2197 0x00ff no byte-order conversion is performed. Make sure you specify
2198 the information in the byte order expected by the receiver.
2199 --data-string string (Append custom string to sent packets)
2201 This option lets you include a regular string as payload in sent
2202 packets. string can contain any string. However, note that some
2203 characters may depend on your system's locale and the receiver may
2204 not see the same information. Also, make sure you enclose the
2205 string in double quotes and escape any special characters from the
2206 shell. Examples: --data-string "Scan conducted by Security Ops,
2207 extension 7192" or --data-string "Ph34r my l33t skills". Keep in
2208 mind that nobody is likely to actually see any comments left by
2209 this option unless they are carefully monitoring the network with a
2210 sniffer or custom IDS rules.
2211 --data-length number (Append random data to sent packets)
2213 Normally Nmap sends minimalist packets containing only a header. So
2214 its TCP packets are generally 40 bytes and ICMP echo requests are
2215 just 28. Some UDP ports and IP protocols get a custom payload by
2216 default. This option tells Nmap to append the given number of
2217 random bytes to most of the packets it sends, and not to use any
2218 protocol-specific payloads. (Use --data-length 0 for no random or
2219 protocol-specific payloads. OS detection (-O) packets are not
2220 affected because accuracy there requires probe consistency, but
2221 most pinging and portscan packets support this. It slows things
2222 down a little, but can make a scan slightly less conspicuous.
2223 --ip-options S|R [route]|L [route]|T|U ... ; --ip-options hex string
2225 (Send packets with specified ip options)
2226 The IP protocol[12] offers several options which may be placed in
2227 packet headers. Unlike the ubiquitous TCP options, IP options are
2228 rarely seen due to practicality and security concerns. In fact,
2229 many Internet routers block the most dangerous options such as
2230 source routing. Yet options can still be useful in some cases for
2231 determining and manipulating the network route to target machines.
2232 For example, you may be able to use the record route option to
2233 determine a path to a target even when more traditional
2234 traceroute-style approaches fail. Or if your packets are being
2235 dropped by a certain firewall, you may be able to specify a
2236 different route with the strict or loose source routing options.
2237 The most powerful way to specify IP options is to simply pass in
2239 values as the argument to --ip-options. Precede each hex number
2240 with \x then the two digits. You may repeat certain characters by
2241 following them with an asterisk and then the number of times you
2242 wish them to repeat. For example, \x01\x07\x04\x00*36\x01 is a hex
2243 string containing 36 NUL bytes.
2244 Nmap also offers a shortcut mechanism for specifying options.
2246 Simply pass the letter R, T, or U to request record-route,
2247 record-timestamp, or both options together, respectively. Loose or
2248 strict source routing may be specified with an L or S followed by a
2249 space and then a space-separated list of IP addresses.
2250 If you wish to see the options in packets sent and received,
2252 specify --packet-trace. For more information and examples of using
2253 IP options with Nmap, see https://seclists.org/nmap-dev/2006/q3/52.
2254 --ttl value (Set IP time-to-live field)
2256 Sets the IPv4 time-to-live field in sent packets to the given
2257 value.
2258 --randomize-hosts (Randomize target host order)
2260 Tells Nmap to shuffle each group of up to 16384 hosts before it
2261 scans them. This can make the scans less obvious to various network
2262 monitoring systems, especially when you combine it with slow timing
2263 options. If you want to randomize over larger group sizes, increase
2264 PING_GROUP_SZ in nmap.h and recompile. An alternative solution is
2265 to generate the target IP list with a list scan (-sL -n -oN
2266 filename), randomize it with a Perl script, then provide the whole
2267 list to Nmap with -iL.
2268 --spoof-mac MAC address, prefix, or vendor name (Spoof MAC address)
2270 Asks Nmap to use the given MAC address
2271 for all of the raw ethernet frames it sends. This option implies
2273 --send-eth to ensure that Nmap actually sends ethernet-level
2274 packets. The MAC given can take several formats. If it is simply
2275 the number 0, Nmap chooses a completely random MAC address for the
2276 session. If the given string is an even number of hex digits (with
2277 the pairs optionally separated by a colon), Nmap will use those as
2278 the MAC. If fewer than 12 hex digits are provided, Nmap fills in
2279 the remainder of the six bytes with random values. If the argument
2280 isn't a zero or hex string, Nmap looks through nmap-mac-prefixes to
2281 find a vendor name containing the given string (it is case
2282 insensitive). If a match is found, Nmap uses the vendor's OUI
2283 (three-byte prefix) and fills out the remaining three bytes
2284 randomly. Valid --spoof-mac argument examples are Apple, 0,
2285 01:02:03:04:05:06, deadbeefcafe, 0020F2, and Cisco. This option
2286 only affects raw packet scans such as SYN scan or OS detection, not
2287 connection-oriented features such as version detection or the Nmap
2288 Scripting Engine.
2289 --proxies Comma-separated list of proxy URLs (Relay TCP connections
2291 through a chain of proxies)
2292 Asks Nmap to establish TCP connections with a final target through
2293 supplied chain of one or more HTTP or SOCKS4 proxies. Proxies can
2294 help hide the true source of a scan or evade certain firewall
2295 restrictions, but they can hamper scan performance by increasing
2296 latency. Users may need to adjust Nmap timeouts and other scan
2297 parameters accordingly. In particular, a lower --max-parallelism
2298 may help because some proxies refuse to handle as many concurrent
2299 connections as Nmap opens by default.
2300 This option takes a list of proxies as argument, expressed as URLs
2302 in the format proto://host:port. Use commas to separate node URLs
2303 in a chain. No authentication is supported yet. Valid protocols are
2304 HTTP and SOCKS4.
2305 Warning: this feature is still under development and has
2307 limitations. It is implemented within the nsock library and thus
2308 has no effect on the ping, port scanning and OS discovery phases of
2309 a scan. Only NSE and version scan benefit from this option so far—
2310 other features may disclose your true address. SSL connections are
2311 not yet supported, nor is proxy-side DNS resolution (hostnames are
2312 always resolved by Nmap).
2313 --badsum (Send packets with bogus TCP/UDP checksums)
2315 Asks Nmap to use an invalid TCP, UDP or SCTP checksum for packets
2316 sent to target hosts. Since virtually all host IP stacks properly
2317 drop these packets, any responses received are likely coming from a
2318 firewall or IDS that didn't bother to verify the checksum. For more
2319 details on this technique, see https://nmap.org/p60-12.html
2320 --adler32 (Use deprecated Adler32 instead of CRC32C for SCTP checksums)
2322 Asks Nmap to use the deprecated Adler32 algorithm for calculating
2323 the SCTP checksum. If --adler32 is not given, CRC-32C (Castagnoli)
2324 is used. RFC 2960[13] originally defined Adler32 as checksum
2325 algorithm for SCTP; RFC 4960[6] later redefined the SCTP checksums
2326 to use CRC-32C. Current SCTP implementations should be using
2327 CRC-32C, but in order to elicit responses from old, legacy SCTP
2328 implementations, it may be preferable to use Adler32.
2329
2331 Any security tool is only as useful as the output it generates. Complex
2332 tests and algorithms are of little value if they aren't presented in an
2333 organized and comprehensible fashion. Given the number of ways Nmap is
2334 used by people and other software, no single format can please
2335 everyone. So Nmap offers several formats, including the interactive
2336 mode for humans to read directly and XML for easy parsing by software.
2337 In addition to offering different output formats, Nmap provides options
2339 for controlling the verbosity of output as well as debugging messages.
2340 Output types may be sent to standard output or to named files, which
2341 Nmap can append to or clobber. Output files may also be used to resume
2342 aborted scans.
2343 Nmap makes output available in five different formats. The default is
2345 called interactive output, and it is sent to standard output (stdout).
2346 There is also normal output, which is similar to interactive except
2347 that it displays less runtime information and warnings since it is
2348 expected to be analyzed after the scan completes rather than
2349 interactively.
2350 XML output is one of the most important output types, as it can be
2352 converted to HTML, easily parsed by programs such as Nmap graphical
2353 user interfaces, or imported into databases.
2354 The two remaining output types are the simple grepable output which
2356 includes most information for a target host on a single line, and
2357 sCRiPt KiDDi3 0utPUt for users who consider themselves |<-r4d.
2358 While interactive output is the default and has no associated
2360 command-line options, the other four format options use the same
2361 syntax. They take one argument, which is the filename that results
2362 should be stored in. Multiple formats may be specified, but each format
2363 may only be specified once. For example, you may wish to save normal
2364 output for your own review while saving XML of the same scan for
2365 programmatic analysis. You might do this with the options -oX
2366 myscan.xml -oN myscan.nmap. While this chapter uses the simple names
2367 like myscan.xml for brevity, more descriptive names are generally
2368 recommended. The names chosen are a matter of personal preference,
2369 though I use long ones that incorporate the scan date and a word or two
2370 describing the scan, placed in a directory named after the company I'm
2371 scanning.
2372 While these options save results to files, Nmap still prints
2374 interactive output to stdout as usual. For example, the command nmap
2375 -oX myscan.xml target prints XML to myscan.xml and fills standard
2376 output with the same interactive results it would have printed if -oX
2377 wasn't specified at all. You can change this by passing a hyphen
2378 character as the argument to one of the format types. This causes Nmap
2379 to deactivate interactive output, and instead print results in the
2380 format you specified to the standard output stream. So the command nmap
2381 -oX - target will send only XML output to stdout. Serious errors may
2382 still be printed to the normal error stream, stderr.
2383 Unlike some Nmap arguments, the space between the logfile option flag
2385 (such as -oX) and the filename or hyphen is mandatory. If you omit the
2386 flags and give arguments such as -oG- or -oXscan.xml, a backwards
2387 compatibility feature of Nmap will cause the creation of normal format
2388 output files named G- and Xscan.xml respectively.
2389 All of these arguments support strftime-like conversions in the
2391 filename. %H, %M, %S, %m, %d, %y, and %Y are all exactly the same as
2392 in strftime. %T is the same as %H%M%S, %R is the same as %H%M, and %D
2393 is the same as %m%d%y. A % followed by any other character just yields
2394 that character (%% gives you a percent symbol). So -oX 'scan-%T-%D.xml'
2395 will use an XML file with a name in the form of scan-144840-121307.xml.
2396 Nmap also offers options to control scan verbosity and to append to
2398 output files rather than clobbering them. All of these options are
2399 described below.
2400 Nmap Output Formats
2402 -oN filespec (normal output)
2404 Requests that normal output be directed to the given filename. As
2405 discussed above, this differs slightly from interactive output.
2406 -oX filespec (XML output)
2408 Requests that XML output be directed to the given filename. Nmap
2409 includes a document type definition (DTD) which allows XML parsers
2410 to validate Nmap XML output. While it is primarily intended for
2411 programmatic use, it can also help humans interpret Nmap XML
2412 output. The DTD defines the legal elements of the format, and often
2413 enumerates the attributes and values they can take on. The latest
2414 version is always available from
2415 https://svn.nmap.org/nmap/docs/nmap.dtd.
2416 XML offers a stable format that is easily parsed by software. Free
2418 XML parsers are available for all major computer languages,
2419 including C/C++, Perl, Python, and Java. People have even written
2420 bindings for most of these languages to handle Nmap output and
2421 execution specifically. Examples are Nmap::Scanner[14] and
2422 Nmap::Parser[15] in Perl CPAN. In almost all cases that a
2423 non-trivial application interfaces with Nmap, XML is the preferred
2424 format.
2425 The XML output references an XSL stylesheet which can be used to
2427 format the results as HTML. The easiest way to use this is simply
2428 to load the XML output in a web browser such as Firefox or IE. By
2429 default, this will only work on the machine you ran Nmap on (or a
2430 similarly configured one) due to the hard-coded nmap.xsl filesystem
2431 path. Use the --webxml or --stylesheet options to create portable
2432 XML files that render as HTML on any web-connected machine.
2433 -oS filespec (ScRipT KIdd|3 oUTpuT)
2435 Script kiddie output is like interactive output, except that it is
2436 post-processed to better suit the l33t HaXXorZ who previously
2437 looked down on Nmap due to its consistent capitalization and
2438 spelling. Humor impaired people should note that this option is
2439 making fun of the script kiddies before flaming me for supposedly
2440 “helping them”.
2441 -oG filespec (grepable output)
2443 This output format is covered last because it is deprecated. The
2444 XML output format is far more powerful, and is nearly as convenient
2445 for experienced users. XML is a standard for which dozens of
2446 excellent parsers are available, while grepable output is my own
2447 simple hack. XML is extensible to support new Nmap features as they
2448 are released, while I often must omit those features from grepable
2449 output for lack of a place to put them.
2450 Nevertheless, grepable output is still quite popular. It is a
2452 simple format that lists each host on one line and can be trivially
2453 searched and parsed with standard Unix tools such as grep, awk,
2454 cut, sed, diff, and Perl. Even I usually use it for one-off tests
2455 done at the command line. Finding all the hosts with the SSH port
2456 open or that are running Solaris takes only a simple grep to
2457 identify the hosts, piped to an awk or cut command to print the
2458 desired fields.
2459 Grepable output consists of comments (lines starting with a pound
2461 (#)) and target lines. A target line includes a combination of six
2462 labeled fields, separated by tabs and followed with a colon. The
2463 fields are Host, Ports, Protocols, Ignored State, OS, Seq Index, IP
2464 ID, and Status.
2465 The most important of these fields is generally Ports, which gives
2467 details on each interesting port. It is a comma separated list of
2468 port entries. Each port entry represents one interesting port, and
2469 takes the form of seven slash (/) separated subfields. Those
2470 subfields are: Port number, State, Protocol, Owner, Service, SunRPC
2471 info, and Version info.
2472 As with XML output, this man page does not allow for documenting
2474 the entire format. A more detailed look at the Nmap grepable output
2475 format is available from
2476 https://nmap.org/book/output-formats-grepable-output.html.
2477 -oA basename (Output to all formats)
2479 As a convenience, you may specify -oA basename to store scan
2480 results in normal, XML, and grepable formats at once. They are
2481 stored in basename.nmap, basename.xml, and basename.gnmap,
2482 respectively. As with most programs, you can prefix the filenames
2483 with a directory path, such as ~/nmaplogs/foocorp/ on Unix or
2484 c:\hacking\sco on Windows.
2485 Verbosity and debugging options
2487 -v (Increase verbosity level), -vlevel (Set verbosity level)
2489 Increases the verbosity level, causing Nmap to print more
2490 information about the scan in progress. Open ports are shown as
2491 they are found and completion time estimates are provided when Nmap
2492 thinks a scan will take more than a few minutes. Use it twice or
2493 more for even greater verbosity: -vv, or give a verbosity level
2494 directly, for example -v3.
2495 Most changes only affect interactive output, and some also affect
2497 normal and script kiddie output. The other output types are meant
2498 to be processed by machines, so Nmap can give substantial detail by
2499 default in those formats without fatiguing a human user. However,
2500 there are a few changes in other modes where output size can be
2501 reduced substantially by omitting some detail. For example, a
2502 comment line in the grepable output that provides a list of all
2503 ports scanned is only printed in verbose mode because it can be
2504 quite long.
2505 -d (Increase debugging level), -dlevel (Set debugging level)
2507 When even verbose mode doesn't provide sufficient data for you,
2508 debugging is available to flood you with much more! As with the
2509 verbosity option (-v), debugging is enabled with a command-line
2510 flag (-d) and the debug level can be increased by specifying it
2511 multiple times, as in -dd, or by setting a level directly. For
2512 example, -d9 sets level nine. That is the highest effective level
2513 and will produce thousands of lines unless you run a very simple
2514 scan with very few ports and targets.
2515 Debugging output is useful when a bug is suspected in Nmap, or if
2517 you are simply confused as to what Nmap is doing and why. As this
2518 feature is mostly intended for developers, debug lines aren't
2519 always self-explanatory. You may get something like: Timeout vals:
2520 srtt: -1 rttvar: -1 to: 1000000 delta 14987 ==> srtt: 14987 rttvar:
2521 14987 to: 100000. If you don't understand a line, your only
2522 recourses are to ignore it, look it up in the source code, or
2523 request help from the development list (nmap-dev). Some lines are
2524 self explanatory, but the messages become more obscure as the debug
2525 level is increased.
2526 --reason (Host and port state reasons)
2528 Shows the reason each port is set to a specific state and the
2529 reason each host is up or down. This option displays the type of
2530 the packet that determined a port or hosts state. For example, A
2531 RST packet from a closed port or an echo reply from an alive host.
2532 The information Nmap can provide is determined by the type of scan
2533 or ping. The SYN scan and SYN ping (-sS and -PS) are very detailed,
2534 but the TCP connect scan (-sT) is limited by the implementation of
2535 the connect system call. This feature is automatically enabled by
2536 the debug option (-d) and the results are stored in XML log files
2537 even if this option is not specified.
2538 --stats-every time (Print periodic timing stats)
2540 Periodically prints a timing status message after each interval of
2541 time. The time is a specification of the kind described in the
2542 section called “TIMING AND PERFORMANCE”; so for example, use
2543 --stats-every 10s to get a status update every 10 seconds. Updates
2544 are printed to interactive output (the screen) and XML output.
2545 --packet-trace (Trace packets and data sent and received)
2547 Causes Nmap to print a summary of every packet sent or received.
2548 This is often used for debugging, but is also a valuable way for
2549 new users to understand exactly what Nmap is doing under the
2550 covers. To avoid printing thousands of lines, you may want to
2551 specify a limited number of ports to scan, such as -p20-30. If you
2552 only care about the goings on of the version detection subsystem,
2553 use --version-trace instead. If you only care about script tracing,
2554 specify --script-trace. With --packet-trace, you get all of the
2555 above.
2556 --open (Show only open (or possibly open) ports)
2558 Sometimes you only care about ports you can actually connect to
2559 (open ones), and don't want results cluttered with closed,
2560 filtered, and closed|filtered ports. Output customization is
2561 normally done after the scan using tools such as grep, awk, and
2562 Perl, but this feature was added due to overwhelming requests.
2563 Specify --open to only see hosts with at least one open,
2564 open|filtered, or unfiltered port, and only see ports in those
2565 states. These three states are treated just as they normally are,
2566 which means that open|filtered and unfiltered may be condensed into
2567 counts if there are an overwhelming number of them.
2568 Beginning with Nmap 7.40, the --open option implies
2570 --defeat-rst-ratelimit, because that option only affects closed and
2572 filtered ports, which are hidden by --open.
2573 --iflist (List interfaces and routes)
2575 Prints the interface list and system routes as detected by Nmap and
2576 quits. This is useful for debugging routing problems or device
2577 mischaracterization (such as Nmap treating a PPP connection as
2578 ethernet).
2579 Miscellaneous output options
2581 --append-output (Append to rather than clobber output files)
2583 When you specify a filename to an output format flag such as -oX or
2584 -oN, that file is overwritten by default. If you prefer to keep the
2585 existing content of the file and append the new results, specify
2586 the --append-output option. All output filenames specified in that
2587 Nmap execution will then be appended to rather than clobbered. This
2588 doesn't work well for XML (-oX) scan data as the resultant file
2589 generally won't parse properly until you fix it up by hand.
2590 --resume filename (Resume aborted scan)
2592 Some extensive Nmap runs take a very long time—on the order of
2593 days. Such scans don't always run to completion. Restrictions may
2594 prevent Nmap from being run during working hours, the network could
2595 go down, the machine Nmap is running on might suffer a planned or
2596 unplanned reboot, or Nmap itself could crash. The administrator
2597 running Nmap could cancel it for any other reason as well, by
2598 pressing ctrl-C. Restarting the whole scan from the beginning may
2599 be undesirable. Fortunately, if scan output files were kept, the
2600 user can ask Nmap to resume scanning with the target it was working
2601 on when execution ceased. Simply specify the --resume option and
2602 pass the output file as its argument. No other arguments are
2603 permitted, as Nmap parses the output file to use the same ones
2604 specified previously. Simply call Nmap as nmap --resume
2605 logfilename. Nmap will append new results to the data files
2606 specified in the previous execution. Scans can be resumed from any
2607 of the 3 major output formats: Normal, Grepable, or XML
2608 --noninteractive (Disable runtime interactions)
2610 At times, such as when running Nmap in a shell background, it might
2611 be undesirable for Nmap to monitor and respond to user keyboard
2612 input when running. (See the section called “RUNTIME INTERACTION”
2613 about how to control Nmap during a scan.) Use option
2614 --noninteractive to prevent Nmap taking control of the terminal.
2615 --stylesheet path or URL (Set XSL stylesheet to transform XML output)
2617 Nmap ships with an XSL stylesheet named nmap.xsl for viewing or
2618 translating XML output to HTML. The XML output includes an
2619 xml-stylesheet directive which points to nmap.xml where it was
2620 initially installed by Nmap. Run the XML file through an XSLT
2621 processor such as xsltproc[16] to produce an HTML file. Directly
2622 opening the XML file in a browser no longer works well because
2623 modern browsers limit the locations a stylesheet may be loaded
2624 from. If you wish to use a different stylesheet, specify it as the
2625 argument to --stylesheet. You must pass the full pathname or URL.
2626 One common invocation is --stylesheet
2627 https://nmap.org/svn/docs/nmap.xsl. This tells an XSLT processor to
2628 load the latest version of the stylesheet from Nmap.Org. The
2629 --webxml option does the same thing with less typing and
2630 memorization. Loading the XSL from Nmap.Org makes it easier to view
2631 results on a machine that doesn't have Nmap (and thus nmap.xsl)
2632 installed. So the URL is often more useful, but the local
2633 filesystem location of nmap.xsl is used by default for privacy
2634 reasons.
2635 --webxml (Load stylesheet from Nmap.Org)
2637 This is a convenience option, nothing more than an alias for
2638 --stylesheet https://nmap.org/svn/docs/nmap.xsl.
2639 --no-stylesheet (Omit XSL stylesheet declaration from XML)
2641 Specify this option to prevent Nmap from associating any XSL
2642 stylesheet with its XML output. The xml-stylesheet directive is
2643 omitted.
2644
2646 This section describes some important (and not-so-important) options
2647 that don't really fit anywhere else.
2648 -6 (Enable IPv6 scanning)
2650 Nmap has IPv6 support for its most popular features. Ping scanning,
2651 port scanning, version detection, and the Nmap Scripting Engine all
2652 support IPv6. The command syntax is the same as usual except that
2653 you also add the -6 option. Of course, you must use IPv6 syntax if
2654 you specify an address rather than a hostname. An address might
2655 look like 3ffe:7501:4819:2000:210:f3ff:fe03:14d0, so hostnames are
2656 recommended. The output looks the same as usual, with the IPv6
2657 address on the “interesting ports” line being the only IPv6
2658 giveaway.
2659 While IPv6 hasn't exactly taken the world by storm, it gets
2661 significant use in some (usually Asian) countries and most modern
2662 operating systems support it. To use Nmap with IPv6, both the
2663 source and target of your scan must be configured for IPv6. If your
2664 ISP (like most of them) does not allocate IPv6 addresses to you,
2665 free tunnel brokers are widely available and work fine with Nmap. I
2666 use the free IPv6 tunnel broker service at
2667 http://www.tunnelbroker.net. Other tunnel brokers are listed at
2668 Wikipedia[17]. 6to4 tunnels are another popular, free approach.
2669 On Windows, raw-socket IPv6 scans are supported only on ethernet
2671 devices (not tunnels), and only on Windows Vista and later. Use the
2672 --unprivileged option in other situations.
2673 -A (Aggressive scan options)
2675 This option enables additional advanced and aggressive options.
2676 Presently this enables OS detection (-O), version scanning (-sV),
2677 script scanning (-sC) and traceroute (--traceroute). More features
2678 may be added in the future. The point is to enable a comprehensive
2679 set of scan options without people having to remember a large set
2680 of flags. However, because script scanning with the default set is
2681 considered intrusive, you should not use -A against target networks
2682 without permission. This option only enables features, and not
2683 timing options (such as -T4) or verbosity options (-v) that you
2684 might want as well. Options which require privileges (e.g. root
2685 access) such as OS detection and traceroute will only be enabled if
2686 those privileges are available.
2687 --datadir directoryname (Specify custom Nmap data file location)
2689 Nmap obtains some special data at runtime in files named
2690 nmap-service-probes, nmap-services, nmap-protocols, nmap-rpc,
2691 nmap-mac-prefixes, and nmap-os-db. If the location of any of these
2692 files has been specified (using the --servicedb or --versiondb
2693 options), that location is used for that file. After that, Nmap
2694 searches these files in the directory specified with the --datadir
2695 option (if any). Any files not found there, are searched for in the
2696 directory specified by the NMAPDIR environment variable. Next comes
2697 ~/.nmap for real and effective UIDs; or on Windows,
2698 HOME\AppData\Roaming\nmap (where HOME is the user's home directory,
2699 like C:\Users\user). This is followed by the location of the nmap
2700 executable and the same location with ../share/nmap appended. Then
2701 a compiled-in location such as /usr/local/share/nmap or
2702 /usr/share/nmap.
2703 --servicedb services file (Specify custom services file)
2705 Asks Nmap to use the specified services file rather than the
2706 nmap-services data file that comes with Nmap. Using this option
2707 also causes a fast scan (-F) to be used. See the description for
2708 --datadir for more information on Nmap's data files.
2709 --versiondb service probes file (Specify custom service probes file)
2711 Asks Nmap to use the specified service probes file rather than the
2712 nmap-service-probes data file that comes with Nmap. See the
2713 description for --datadir for more information on Nmap's data
2714 files.
2715 --send-eth (Use raw ethernet sending)
2717 Asks Nmap to send packets at the raw ethernet (data link) layer
2718 rather than the higher IP (network) layer. By default, Nmap chooses
2719 the one which is generally best for the platform it is running on.
2720 Raw sockets (IP layer) are generally most efficient for Unix
2721 machines, while ethernet frames are required for Windows operation
2722 since Microsoft disabled raw socket support. Nmap still uses raw IP
2723 packets on Unix despite this option when there is no other choice
2724 (such as non-ethernet connections).
2725 --send-ip (Send at raw IP level)
2727 Asks Nmap to send packets via raw IP sockets rather than sending
2728 lower level ethernet frames. It is the complement to the --send-eth
2729 option discussed previously.
2730 --privileged (Assume that the user is fully privileged)
2732 Tells Nmap to simply assume that it is privileged enough to perform
2733 raw socket sends, packet sniffing, and similar operations that
2734 usually require root privileges on Unix systems. By default Nmap
2735 quits if such operations are requested but geteuid is not zero.
2736 --privileged is useful with Linux kernel capabilities and similar
2737 systems that may be configured to allow unprivileged users to
2738 perform raw-packet scans. Be sure to provide this option flag
2739 before any flags for options that require privileges (SYN scan, OS
2740 detection, etc.). The NMAP_PRIVILEGED environment variable may be
2741 set as an equivalent alternative to --privileged.
2742 --unprivileged (Assume that the user lacks raw socket privileges)
2744 This option is the opposite of --privileged. It tells Nmap to treat
2745 the user as lacking network raw socket and sniffing privileges.
2746 This is useful for testing, debugging, or when the raw network
2747 functionality of your operating system is somehow broken. The
2748 NMAP_UNPRIVILEGED environment variable may be set as an equivalent
2749 alternative to --unprivileged.
2750 --release-memory (Release memory before quitting)
2752 This option is only useful for memory-leak debugging. It causes
2753 Nmap to release allocated memory just before it quits so that
2754 actual memory leaks are easier to spot. Normally Nmap skips this as
2755 the OS does this anyway upon process termination.
2756 -V; --version (Print version number)
2758 Prints the Nmap version number and exits.
2759 -h; --help (Print help summary page)
2761 Prints a short help screen with the most common command flags.
2762 Running Nmap without any arguments does the same thing.
2763
2765 During the execution of Nmap, all key presses are captured. This allows
2766 you to interact with the program without aborting and restarting it.
2767 Certain special keys will change options, while any other keys will
2768 print out a status message telling you about the scan. The convention
2769 is that lowercase letters increase the amount of printing, and
2770 uppercase letters decrease the printing. You may also press ‘?’ for
2771 help.
2772 v / V
2774 Increase / decrease the verbosity level
2775 d / D
2777 Increase / decrease the debugging Level
2778 p / P
2780 Turn on / off packet tracing
2781 ?
2783 Print a runtime interaction help screen
2784 Anything else
2786 Print out a status message like this:
2787 Stats: 0:00:07 elapsed; 20 hosts completed (1 up), 1 undergoing Service Scan
2789 Service scan Timing: About 33.33% done; ETC: 20:57 (0:00:12 remaining)
2790
2792 Here are some Nmap usage examples, from the simple and routine to a
2793 little more complex and esoteric. Some actual IP addresses and domain
2794 names are used to make things more concrete. In their place you should
2795 substitute addresses/names from your own network. While I don't think
2796 port scanning other networks is or should be illegal, some network
2797 administrators don't appreciate unsolicited scanning of their networks
2798 and may complain. Getting permission first is the best approach.
2799 For testing purposes, you have permission to scan the host
2801 scanme.nmap.org. This permission only includes scanning via Nmap and
2802 not testing exploits or denial of service attacks. To conserve
2803 bandwidth, please do not initiate more than a dozen scans against that
2804 host per day. If this free scanning target service is abused, it will
2805 be taken down and Nmap will report Failed to resolve given hostname/IP:
2806 scanme.nmap.org. These permissions also apply to the hosts
2807 scanme2.nmap.org, scanme3.nmap.org, and so on, though those hosts do
2808 not currently exist.
2809 nmap -v scanme.nmap.org
2811 This option scans all reserved TCP ports on the machine scanme.nmap.org
2813 . The -v option enables verbose mode.
2814 nmap -sS -O scanme.nmap.org/24
2816 Launches a stealth SYN scan against each machine that is up out of the
2819 256 IPs on the /24 sized network where Scanme resides. It also tries to
2820 determine what operating system is running on each host that is up and
2821 running. This requires root privileges because of the SYN scan and OS
2822 detection.
2823 nmap -sV -p 22,53,110,143,4564 198.116.0-255.1-127
2825 Launches host enumeration and a TCP scan at the first half of each of
2827 the 255 possible eight-bit subnets in the 198.116.0.0/16 address space.
2828 This tests whether the systems run SSH, DNS, POP3, or IMAP on their
2829 standard ports, or anything on port 4564. For any of these ports found
2830 open, version detection is used to determine what application is
2831 running.
2832 nmap -v -iR 100000 -Pn -p 80
2834 Asks Nmap to choose 100,000 hosts at random and scan them for web
2837 servers (port 80). Host enumeration is disabled with -Pn since first
2838 sending a couple probes to determine whether a host is up is wasteful
2839 when you are only probing one port on each target host anyway.
2840 nmap -Pn -p80 -oX logs/pb-port80scan.xml -oG logs/pb-port80scan.gnmap
2842 216.163.128.20/20
2843 This scans 4096 IPs for any web servers (without pinging them) and
2846 saves the output in grepable and XML formats.
2847
2849 While this reference guide details all material Nmap options, it can't
2850 fully demonstrate how to apply those features to quickly solve
2851 real-world tasks. For that, we released Nmap Network Scanning: The
2852 Official Nmap Project Guide to Network Discovery and Security Scanning.
2853 Topics include subverting firewalls and intrusion detection systems,
2854 optimizing Nmap performance, and automating common networking tasks
2855 with the Nmap Scripting Engine. Hints and instructions are provided for
2856 common Nmap tasks such as taking network inventory, penetration
2857 testing, detecting rogue wireless access points, and quashing network
2858 worm outbreaks. Examples and diagrams show actual communication on the
2859 wire. More than half of the book is available free online. See
2860 https://nmap.org/book for more information.
2861
2863 Like its author, Nmap isn't perfect. But you can help make it better by
2864 sending bug reports or even writing patches. If Nmap doesn't behave the
2865 way you expect, first upgrade to the latest version available from
2866 https://nmap.org. If the problem persists, do some research to
2867 determine whether it has already been discovered and addressed. Try
2868 searching for the problem or error message on Google since that
2869 aggregates so many forums. If nothing comes of this, create an Issue on
2870 our tracker (http://issues.nmap.org) and/or mail a bug report to
2871 <dev@nmap.org>. If you subscribe to the nmap-dev list before posting,
2872 your message will bypass moderation and get through more quickly.
2873 Subscribe at https://nmap.org/mailman/listinfo/dev. Please include
2874 everything you have learned about the problem, as well as what version
2875 of Nmap you are using and what operating system version it is running
2876 on. Other suggestions for improving Nmap may be sent to the Nmap dev
2877 mailing list as well.
2878 If you are able to write a patch improving Nmap or fixing a bug, that
2880 is even better! Instructions for submitting patches or git pull
2881 requests are available from
2882 https://github.com/nmap/nmap/blob/master/CONTRIBUTING.md
2883 Particularly sensitive issues such as a security reports may be sent
2885 directly to Nmap's author Fyodor directly at <fyodor@nmap.org>. All
2886 other reports and comments should use the dev list or issue tracker
2887 instead because more people read, follow, and respond to those.
2888
2890 Gordon “Fyodor” Lyon <fyodor@nmap.org> wrote and released Nmap in 1997.
2891 Since then, hundreds of people have made valuable contributions, as
2892 detailed in the CHANGELOG file distributed with Nmap and also available
2893 from https://nmap.org/changelog.html. David Fifield and Daniel Miller
2894 deserve special recognition for their enormous multi-year
2895 contributions!
2896
2898 Nmap Copyright and Licensing
2899 The Nmap Security Scanner is (C) 1996–2022 Nmap Software LLC ("The Nmap
2900 Project"). Nmap is also a registered trademark of the Nmap Project. It
2901 is published under the Nmap Public Source License[18]. This generally
2902 allows end users to download and use Nmap for free. It doesn't allow
2903 Nmap to be used and redistributed within commercial software or
2904 hardware products (including appliances, virtual machines, and
2905 traditional applications). We fund the project by selling a special
2906 Nmap OEM Edition for this purpose, as described at
2907 https://nmap.org/oem. Hundreds of large and small software vendors have
2908 already purchased OEM licenses to embed Nmap technology such as host
2909 discovery, port scanning, OS detection, version detection, and the Nmap
2910 Scripting Engine within their products.
2911 The Nmap Project has permission to redistribute Npcap, a packet
2913 capturing driver and library for the Microsoft Windows platform. Npcap
2914 is a separate work with it's own license rather than this Nmap license.
2915 Since the Npcap license does not permit redistribution without special
2916 permission, our Nmap Windows binary packages which contain Npcap may
2917 not be redistributed without special permission.
2918 Even though the NPSL is based on GPLv2, it contains different
2920 provisions and is not directly compatible. It is incompatible with some
2921 other open source licenses as well. In some cases we can relicense
2922 portions of Nmap or grant special permissions to use it in other open
2923 source software. Please contact fyodor@nmap.org with any such requests.
2924 Similarly, we don't incorporate incompatible open source software into
2925 Nmap without special permission from the copyright holders.
2926 If you have received a written license agreement or contract for Nmap
2928 (such as an Nmap OEM license[19]) stating terms other than these, you
2929 may choose to use and redistribute Nmap under those terms instead.
2930 Creative Commons License for this Nmap Guide
2932 This Nmap Reference Guide is (C) 2005–2022 Nmap Software LLC. It is
2933 hereby placed under version 3.0 of the Creative Commons Attribution
2934 License[20]. This allows you redistribute and modify the work as you
2935 desire, as long as you credit the original source. Alternatively, you
2936 may choose to treat this document as falling under the same license as
2937 Nmap itself (discussed previously).
2938 Source Code Availability and Community Contributions
2940 Source is provided to this software because we believe users have a
2941 right to know exactly what a program is going to do before they run it.
2942 This also allows you to audit the software for security holes.
2943 Source code also allows you to port Nmap to new platforms, fix bugs,
2945 and add new features. You are highly encouraged to submit your changes
2946 as Github Pull Requests (PR) or send them to <dev@nmap.org> for
2947 possible incorporation into the main distribution. By submitting such
2948 changes, it is assumed that you are offering the Nmap Project the
2949 unlimited, non-exclusive right to reuse, modify, and relicense the
2950 code. This is important because the inability to relicense code has
2951 caused devastating problems for other Free Software projects (such as
2952 KDE and NASM). We also sell commercial licenses to Nmap OEM[21]. If you
2953 wish to specify special license conditions of your contributions, just
2954 say so when you send them.
2955 No Warranty
2957 This program is distributed in the hope that it will be useful, but
2958 WITHOUT ANY WARRANTY; without even the implied warranty of
2959 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
2960 It should also be noted that Nmap has occasionally been known to crash
2962 poorly written applications, TCP/IP stacks, and even operating systems.
2963 While this is extremely rare, it is important to keep in mind. Nmap
2964 should never be run against mission critical systems unless you are
2965 prepared to suffer downtime. We acknowledge here that Nmap may crash
2966 your systems or networks and we disclaim all liability for any damage
2967 or problems Nmap could cause.
2968 Inappropriate Usage
2970 Because of the slight risk of crashes and because a few black hats like
2971 to use Nmap for reconnaissance prior to attacking systems, there are
2972 administrators who become upset and may complain when their system is
2973 scanned. Thus, it is often advisable to request permission before doing
2974 even a light scan of a network.
2975 Nmap should never be installed with special privileges (e.g. suid
2977 root). That would open up a major security vulnerability as other
2978 users on the system (or attackers) could use it for privilege
2979 escalation.
2980 Nmap is not designed, manufactured, or intended for use in hazardous
2982 environments requiring fail- safe performance where the failure of the
2983 software could lead directly to death, personal injury, or significant
2984 physical or environmental damage.
2985 Third-Party Software and Funding Notices
2987 This product includes software developed by the Apache Software
2988 Foundation[22]. A modified version of the Libpcap portable packet
2989 capture library[23] is distributed along with Nmap. The Windows version
2990 of Nmap utilizes the Libpcap-derived Ncap library[24] instead. Regular
2991 expression support is provided by the PCRE library[25], which is
2992 open-source software, written by Philip Hazel. Certain raw networking
2993 functions use the Libdnet[26] networking library, which was written by
2994 Dug Song. A modified version is distributed with Nmap. Nmap can
2995 optionally link with the OpenSSL cryptography toolkit[27] for SSL
2996 version detection support. The Nmap Scripting Engine uses an embedded
2997 version of the Lua programming language[28]. The Liblinear linear
2998 classification library[29] is used for our IPv6 OS detection machine
2999 learning techniques[30].
3000 All of the third-party software described in this paragraph is freely
3002 redistributable under BSD-style software licenses.
3003 Binary packages for Windows and Mac OS X include support libraries
3005 necessary to run Zenmap and Ndiff with Python and PyGTK. (Unix
3006 platforms commonly make these libraries easy to install, so they are
3007 not part of the packages.) A listing of these support libraries and
3008 their licenses is included in the LICENSES files.
3009 This software was supported in part through the Google Summer of
3011 Code[31] and the DARPA CINDER program[32] (DARPA-BAA-10-84).
3012 United States Export Control
3014 Nmap only uses encryption when compiled with the optional OpenSSL
3015 support and linked with OpenSSL. When compiled without OpenSSL support,
3016 the Nmap Project believes that Nmap is not subject to U.S. Export
3017 Administration Regulations (EAR)[33] export control. As such, there is
3018 no applicable ECCN (export control classification number) and
3019 exportation does not require any special license, permit, or other
3020 governmental authorization.
3021 When compiled with OpenSSL support or distributed as source code, the
3023 Nmap Project believes that Nmap falls under U.S. ECCN 5D002[34]
3024 (“Information Security Software”). We distribute Nmap under the TSU
3025 exception for publicly available encryption software defined in EAR
3026 740.13(e)[35].
3027
3029 1. Nmap Network Scanning: The Official Nmap Project Guide to Network
3030 Discovery and Security Scanning
3031 https://nmap.org/book/
3032 2. RFC 1122
3034 http://www.rfc-editor.org/rfc/rfc1122.txt
3035 3. RFC 792
3037 http://www.rfc-editor.org/rfc/rfc792.txt
3038 4. RFC 950
3040 http://www.rfc-editor.org/rfc/rfc950.txt
3041 5. UDP
3043 http://www.rfc-editor.org/rfc/rfc768.txt
3044 6. SCTP
3046 http://www.rfc-editor.org/rfc/rfc4960.txt
3047 7. TCP RFC
3049 http://www.rfc-editor.org/rfc/rfc793.txt
3050 8. RFC 959
3052 http://www.rfc-editor.org/rfc/rfc959.txt
3053 9. RFC 1323
3055 http://www.rfc-editor.org/rfc/rfc1323.txt
3056 10. Lua programming language
3058 http://lua.org
3059 11. precedence
3061 http://www.lua.org/manual/5.1/manual.html#2.5.3
3062 12. IP protocol
3064 http://www.rfc-editor.org/rfc/rfc791.txt
3065 13. RFC 2960
3067 http://www.rfc-editor.org/rfc/rfc2960.txt
3068 14. Nmap::Scanner
3070 http://sourceforge.net/projects/nmap-scanner/
3071 15. Nmap::Parser
3073 http://nmapparser.wordpress.com/
3074 16. xsltproc
3076 http://xmlsoft.org/XSLT/
3077 17. listed at Wikipedia
3079 http://en.wikipedia.org/wiki/List_of_IPv6_tunnel_brokers
3080 18. Nmap Public Source License
3082 https://nmap.org/npsl
3083 19. Nmap OEM license
3085 https://nmap.org/oem/
3086 20. Creative Commons Attribution License
3088 http://creativecommons.org/licenses/by/3.0/
3089 21. Nmap OEM
3091 https://nmap.org/oem
3092 22. Apache Software Foundation
3094 https://www.apache.org
3095 23. Libpcap portable packet capture library
3097 https://www.tcpdump.org
3098 24. Ncap library
3100 https://npcap.com
3101 25. PCRE library
3103 https://pcre.org
3104 26. Libdnet
3106 http://libdnet.sourceforge.net
3107 27. OpenSSL cryptography toolkit
3109 https://openssl.org
3110 28. Lua programming language
3112 https://lua.org
3113 29. Liblinear linear classification library
3115 https://www.csie.ntu.edu.tw/~cjlin/liblinear/
3116 30. IPv6 OS detection machine learning techniques
3118 https://nmap.org/book/osdetect-guess.html#osdetect-guess-ipv6
3119 31. Google Summer of Code
3121 https://nmap.org/soc/
3122 32. DARPA CINDER program
3124 https://www.fbo.gov/index?s=opportunity&mode=form&id=585e02a51f77af5cb3c9e06b9cc82c48&tab=core&_cview=1
3125 33. Export Administration Regulations (EAR)
3127 https://www.bis.doc.gov/index.php/regulations/export-administration-regulations-ear
3128 34. 5D002
3130 https://www.bis.doc.gov/index.php/documents/regulations-docs/federal-register-notices/federal-register-2014/951-ccl5-pt2/file
3131 35. EAR 740.13(e)
3133 https://www.bis.doc.gov/index.php/documents/regulations-docs/2341-740-2/file
3134Nmap 08/31/2022 NMAP(1)