View source for Sendmail

Step by step instructions for setting up '''fail2ban for sendmail'''.

==Create the filter==
First, create a filter file for sendmail, typically <code>filter.d/sendmail.conf</code>, with the following content:

<pre><nowiki>
# Fail2Ban configuration file
#
# Source: http://www.the-art-of-web.com/system/fail2ban-sendmail/
# Contibutors: Gutza, the SASL regex
#
# $Revision: 0 $
#

[Definition]

# Option:  failregex
# Notes.:  regex to match the password failures messages in the logfile. The
#          host must be matched by a group named "host". The tag "<HOST>" can
#          be used for standard IP/hostname matching and is only an alias for
#          (?:::f{4,6}:)?(?P<host>\S+)
# Values:  TEXT
#

failregex = \[<HOST>\] .*to MTA
#            \[<HOST>\] \(may be forged\)
            \[<HOST>\], reject.*\.\.\. Relaying denied
            (User unknown)\n* \[<HOST>\]
            badlogin: .* \[<HOST>\] plaintext .* SASL

# Option:  ignoreregex
# Notes.:  regex to ignore. If this regex matches, the line is ignored.
# Values:  TEXT
#
ignoreregex =
</nowiki></pre>

You may enable the "(may be forged)" line by uncommenting it (remove the hash symbol at the beginning of the line). Observe caution about that particular regular expression, because it might cause bans on legitimate users.

==Define the jail==
Now you need to tell fail2ban what to do with this filter. Edit <code>jail.conf</code> and add the following section:

<pre><nowiki>
[sendmail]
enabled  = true
filter   = sendmail
action   = iptables-multiport[name=sendmail, port="pop3,imap,smtp,pop3s,imaps,smtps", protocol=tcp]
           sendmail-whois[name=sendmail, dest=you@example.com]
logpath  = /var/log/maillog
</nowiki></pre>

Don't forget to change <code>you@example.com</code> with your e-mail address.

[[Category:Configuration]]