1NDIFF(1) User Commands NDIFF(1)
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6 ndiff - Utility to compare the results of Nmap scans
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9 ndiff [options] {a.xml} {b.xml}
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12 Ndiff is a tool to aid in the comparison of Nmap scans. It takes two
13 Nmap XML output files and prints the differences between them. The
14 differences observed are:
15 · Host states (e.g. up to down)
17 · Port states (e.g. open to closed)
19 · Service versions (from -sV)
21 · OS matches (from -O)
23 · Script output
25 Ndiff, like the standard diff utility, compares two scans at a time.
28
30 -h, --help
31 Show a help message and exit.
32 -v, --verbose
34 Include all hosts and ports in the output, not only those that have
35 changed.
36 --text
38 Write output in human-readable text format.
39 --xml
41 Write output in machine-readable XML format. The document structure
42 is defined in the file ndiff.dtd included in the distribution.
43 Any other arguments are taken to be the names of Nmap XML output files.
45 There must be exactly two.
46
48 Let´s use Ndiff to compare the output of two Nmap scans that use
49 different options. In the first, we´ll do a fast scan (-F), which scans
50 fewer ports for speed. In the second, we´ll scan the larger default set
51 of ports, and run an NSE script.
52 # nmap -F scanme.nmap.org -oX scanme-1.xml
54 # nmap --script=html-title scanme.nmap.org -oX scanme-2.xml
55 $ ndiff -v scanme-1.xml scanme-2.xml
56 -Nmap 5.35DC1 at 2010-07-16 12:09
57 +Nmap 5.35DC1 at 2010-07-16 12:13
58 scanme.nmap.org (64.13.134.52):
60 Host is up.
61 -Not shown: 95 filtered ports
62 +Not shown: 993 filtered ports
63 PORT STATE SERVICE VERSION
64 22/tcp open ssh
65 25/tcp closed smtp
66 53/tcp open domain
67 +70/tcp closed gopher
68 80/tcp open http
69 +|_ html-title: Go ahead and ScanMe!
70 113/tcp closed auth
71 +31337/tcp closed Elite
72 Changes are marked by a - or + at the beginning of a line. We can see
74 from the output that the scan without the -F fast scan option found two
75 additional ports: 70 and 31337. The html-title script produced some
76 additional output for port 80. From the port counts, we may infer that
77 the fast scan scanned 100 ports (95 filtered, 3 open, and 2 closed),
78 while the normal scan scanned 1000 (993 filtered, 3 open, and 4
79 closed).
80 The -v (or --verbose) option to Ndiff made it show even the ports that
82 didn´t change, like 22 and 25. Without -v, they would not have been
83 shown.
84
86 There are two output modes: text and XML. Text output is the default,
87 and can also be selected with the --text option. Text output resembles
88 a unified diff of Nmap´s normal terminal output. Each line is preceded
89 by a character indicating whether and how it changed. - means that the
90 line was in the first scan but not in the second; + means it was in the
91 second but not the first. A line that changed is represented by a -
92 line followed by a + line. Lines that did not change are preceded by a
93 blank space.
94 Example 1 is an example of text output. Here, port 80 on the host
96 photos-cache-snc1.facebook.com gained a service version (lighttpd
97 1.5.0). The host at 69.63.179.25 changed its reverse DNS name. The host
98 at 69.63.184.145 was completely absent in the first scan but came up in
99 the second.
100 Example 1. Ndiff text output
102 -Nmap 4.85BETA3 at 2009-03-15 11:00
104 +Nmap 4.85BETA4 at 2009-03-18 11:00
105 photos-cache-snc1.facebook.com (69.63.178.41):
107 Host is up.
108 Not shown: 99 filtered ports
109 PORT STATE SERVICE VERSION
110 -80/tcp open http
111 +80/tcp open http lighttpd 1.5.0
112 -cm.out.snc1.tfbnw.net (69.63.179.25):
114 +mailout-snc1.facebook.com (69.63.179.25):
115 Host is up.
116 Not shown: 100 filtered ports
117 +69.63.184.145:
119 +Host is up.
120 +Not shown: 98 filtered ports
121 +PORT STATE SERVICE VERSION
122 +80/tcp open http Apache httpd 1.3.41.fb1
123 +443/tcp open ssl/http Apache httpd 1.3.41.fb1
124 XML output, intended to be processed by other programs, is selected
126 with the --xml option. It is based on Nmap´s XML output, with a few
127 additional elements to indicate differences. The XML document is
128 enclosed in nmapdiff and scandiff elements. Host differences are
129 enclosed in hostdiff tags and port differences are enclosed in portdiff
130 tags. Inside a hostdiff or portdiff, a and b tags show the state of the
131 host or port in the first scan (a) or the second scan (b).
132 Example 2 shows the XML diff of the same scans shown above in
134 Example 1. Notice how port 80 of photos-cache-snc1.facebook.com is
135 enclosed in portdiff tags. For 69.63.179.25, the old hostname is in a
136 tags and the new is in b. For the new host 69.63.184.145, there is a b
137 in the hostdiff without a corresponding a, indicating that there was no
138 information for the host in the first scan.
139 Example 2. Ndiff XML output
141 <?xml version="1.0" encoding="UTF-8"?>
143 <nmapdiff version="1">
144 <scandiff>
145 <hostdiff>
146 <host>
147 <status state="up"/>
148 <address addr="69.63.178.41" addrtype="ipv4"/>
149 <hostnames>
150 <hostname name="photos-cache-snc1.facebook.com"/>
151 </hostnames>
152 <ports>
153 <extraports count="99" state="filtered"/>
154 <portdiff>
155 <port portid="80" protocol="tcp">
156 <state state="open"/>
157 <a>
158 <service name="http"/>
159 </a>
160 <b>
161 <service name="http" product="lighttpd" version="1.5.0"/>
162 </b>
163 </port>
164 </portdiff>
165 </ports>
166 </host>
167 </hostdiff>
168 <hostdiff>
169 <host>
170 <status state="up"/>
171 <address addr="69.63.179.25" addrtype="ipv4"/>
172 <hostnames>
173 <a>
174 <hostname name="cm.out.snc1.tfbnw.net"/>
175 </a>
176 <b>
177 <hostname name="mailout-snc1.facebook.com"/>
178 </b>
179 </hostnames>
180 <ports>
181 <extraports count="100" state="filtered"/>
182 </ports>
183 </host>
184 </hostdiff>
185 <hostdiff>
186 <b>
187 <host>
188 <status state="up"/>
189 <address addr="69.63.184.145" addrtype="ipv4"/>
190 <ports>
191 <extraports count="98" state="filtered"/>
192 <port portid="80" protocol="tcp">
193 <state state="open"/>
194 <service name="http" product="Apache httpd"
195 version="1.3.41.fb1"/>
196 </port>
197 <port portid="443" protocol="tcp">
198 <state state="open"/>
199 <service name="http" product="Apache httpd" tunnel="ssl"
200 version="1.3.41.fb1"/>
201 </port>
202 </ports>
203 </host>
204 </b>
205 </hostdiff>
206 </scandiff>
207 </nmapdiff>
208
210 Using Nmap, Ndiff, cron, and a shell script, it´s possible to scan a
211 network daily and get email reports of the state of the network and
212 changes since the previous scan. Example 3 shows the script that ties
213 it together.
214 Example 3. Scanning a network periodically with Ndiff and cron
216 #!/bin/sh
218 TARGETS="targets"
219 OPTIONS="-v -T4 -F -sV"
220 date=`date +%F`
221 cd /root/scans
222 nmap $OPTIONS $TARGETS -oA scan-$date > /dev/null
223 if [ -e scan-prev.xml ]; then
224 ndiff scan-prev.xml scan-$date.xml > diff-$date
225 echo "*** NDIFF RESULTS ***"
226 cat diff-$date
227 echo
228 fi
229 echo "*** NMAP RESULTS ***"
230 cat scan-$date.nmap
231 ln -sf scan-$date.xml scan-prev.xml
232 If the script is saved as /root/scan-ndiff.sh, add the following line
234 to root´s crontab:
235 0 12 * * * /root/scan-ndiff.sh
237
240 The exit code indicates whether the scans are equal.
241 · 0 means that the scans are the same in all the aspects Ndiff knows
243 about.
244 · 1 means that the scans differ.
246 · 2 indicates a runtime error, such as the failure to open a file.
248
251 Report bugs to the nmap-dev mailing list at nmap-dev@insecure.org.
252
254 Ndiff started as a project by Michael Pattrick during the 2008 Google
255 Summer of Code. Michael designed the program and led the discussion of
256 its output formats. He wrote versions of the program in Perl and C++,
257 but the summer ended shortly after it was decided to rewrite the
258 program in Python for the sake of Windows (and Zenmap) compatibility.
259 This Python version was written by David Fifield. James Levine
260 released[1] a Perl script named Ndiff with similar functionality in
261 2000.
262
264 David Fifield david@bamsoftware.com
265 Michael Pattrick mpattrick@rhinovirus.org
267
269 http://nmap.org/ndiff/
270
272 1. released
273 http://seclists.org/nmap-hackers/2000/315
274Ndiff 02/11/2011 NDIFF(1)