1SSHGUARD-SETUP(7) SSHGuard Manual SSHGUARD-SETUP(7)
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6 sshguard-setup - setting up SSHGuard on your system
7
9 To set up SSHGuard, write sshguard.conf and set up the backend, if nec‐
10 essary. Configuration options are documented in the sample configura‐
11 tion file. A good starting point is to copy it and make the necessary
12 changes:
13 1. Set BACKEND. You may also need to set it up to work with SSHGuard
15 (see BACKENDS).
16 2. Set FILES, LOGREADER, or both. Alternatively, give sshguard a list
18 of files to monitor as positional arguments on the command-line.
19 Use FILES to specify a space-separated list of log files to monitor.
21 Use LOGREADER to specify a shell command to run to obtain logs. Both
22 settings are ignored if files are given on the command-line.
23 Sample LOGREADER commands for journalctl(1) and macOS 10.12+ are avail‐
25 able in the sample configuration.
26
28 syslog-ng
29 For syslog-ng 2.x, add the following lines to syslog-ng.conf:
30 # pass only entries with auth+authpriv facilities from programs other than sshguard
32 filter sshlogs { facility(auth, authpriv) and not match("sshguard"); };
33 # pass to this process with this template (avoids <ID> prefixes)
34 destination sshguardproc {
35 program("/usr/local/sbin/sshguard"
36 template("$DATE $FULLHOST $MESSAGE\n"));
37 };
38 log { source(src); filter(sshlogs); destination(sshguardproc); };
39 For syslog-ng 3.x, add the following lines to syslog-ng.conf:
41 # enable 3.x mode
43 @version:3.0
44 # pass only entries with auth+authpriv facilities from programs other than sshguard
46 filter f_sshguard { facility(auth, authpriv) and not program("sshguard"); };
47 # pass entries built with this format
48 destination sshguard {
49 program("/usr/sbin/sshguard"
50 template("$DATE $FULLHOST $MSGHDR$MESSAGE\n")
51 );
52 };
53 log { source(src); filter(f_sshguard); destination(sshguard); };
54 After restarting syslog-ng, SSHGuard should start as soon as a log
56 entry with facility auth or authpriv arrives. If you are monitoring
57 services other than sshd, add the appropriate log facilities to sys‐
58 log-ng.conf.
59 metalog
61 Add the following lines to metalog.conf:
62 Stuff to protect from brute force attacks :
64 # for ssh
65 facility = "*"
66 program = "sshd"
67 # other services ...
68 # log to /var/log/sshguard directory
69 logdir = "/var/log/sshguard"
70 After restarting metalog, log entries will appear in /var/log/sshguard.
72 Use log polling to monitor the current log.
73
75 SSHGuard can block attackers using one of several firewall backends
76 that is selected at compile-time.
77 WARNING:
79 Read the documentation for your firewall. Make sure you fully under‐
80 stand each rule or command in the examples below before using them.
81 They may need to be adjusted to suit your particular configuration.
82 pf
84 SSHGuard adds attackers to table <sshguard>. Create the table and block
85 attackers by adding the following lines to pf.conf:
86 table <sshguard> persist
88 block in proto tcp from <sshguard>
89 After reloading the pf configuration, you can inspect the contents of
91 the table using:
92 # pfctl -t sshguard -T show
94 ipfw
96 SSHGuard creates and adds attackers to table 22. The table can be used
97 to block attackers in your ruleset. For example:
98 # ipfw add 5000 reset ip from table\(22\) to me
100 You can inspect the contents of the table using:
102 # ipfw table 22 list
104 firewalld
106 Blocked attackers are added to two ipsets named sshguard4 and ssh‐
107 guard6. The entries in the ipsets are blocked by default in the
108 default firewall zone. Additional firewall zones can be configured
109 using:
110 # firewall-cmd --zone=zone-name --permanent \
112 --add-rich-rule="rule source ipset=sshguard4 drop"
113 # firewall-cmd --zone=zone-name --permanent \
114 --add-rich-rule="rule source ipset=sshguard6 drop"
115 You can inspect the entries in the two ipsets using:
117 # firewall-cmd --permanent --info-ipset=sshguard4
119 # firewall-cmd --permanent --info-ipset=sshguard6
120 ipset
122 Blocked attackers are added to two ipsets named sshguard4 and ssh‐
123 guard6. Nothing is blocked by default, but can used as a source for
124 iptables and other tools. E.g.:
125 # iptables -I INPUT -m set --match-set sshguard4 src -j DROP
127 # ip6tables -I INPUT -m set --match-set sshguard6 src -j DROP
128 netfilter/iptables
130 Create a chain for SSHGuard:
131 # iptables -N sshguard # for IPv4
133 # ip6tables -N sshguard # for IPv6
134 Update the INPUT chain to also pass the traffic to the sshguard chain
136 at the very end of its processing. Specify in --dport all the ports of
137 services your sshguard protects. If you want to prevent attackers from
138 doing any traffic to the host, remove the option completely:
139 # block any traffic from abusers
141 iptables -A INPUT -j sshguard
142 ip6tables -A INPUT -j sshguard
143 Or:
145 # block abusers only for SSH, FTP, POP, IMAP services (use "multiport" module)
147 iptables -A INPUT -m multiport -p tcp --destination-ports 21,22,110,143 -j sshguard
148 ip6tables -A INPUT -m multiport -p tcp --destination-ports 21,22,110,143 -j sshguard
149 Verify that you have NOT a default allow rule passing all ssh traffic
151 higher in the chain. Verify that you have NOT a default deny rule
152 blocking all ssh traffic in your firewall. In either case, you already
153 have the skill to adjust your firewall setup.
154 Here is a sample ruleset that makes sense:
156 iptables -N sshguard
158 # block whatever SSHGuard says be bad ...
159 iptables -A INPUT -j sshguard
160 # enable ssh, dns, http, https
161 iptables -A INPUT -p tcp --dport 22 -j ACCEPT
162 iptables -A INPUT -p udp --dport 53 -j ACCEPT
163 iptables -A INPUT -p tcp --dport 80 -j ACCEPT
164 iptables -A INPUT -p tcp --dport 443 -j ACCEPT
165 # and block everything else (default deny)
166 iptables -P INPUT DROP
167 When rebooting, most systems reset the firewall configuration by
169 default. To preserve your configuration, you usually use the ipta‐
170 bles-save and iptables-restore utilities. However, each Linux variant
171 has its own "right way".
172 nftables
174 SSHGuard creates tables with a high priority and adds attackers to a
175 set automatically.
176 You can inspect the contents of the sets using:
178 # nft list set ip sshguard attackers
180 # nft list set ip6 sshguard attackers
181 Moreover, you can display sshguard's tables with:
183 # nft list table ip sshguard
185 # nft list table ip6 sshguard
186
188 Ignore FILES and monitor these files instead:
189 # sshguard /var/log/auth.log /var/log/maillog
191
193 sshguard(8)
1942.4 May 23, 2019 SSHGUARD-SETUP(7)