fail2ban/config/filter.d/dovecot.conf

# Fail2Ban filter Dovecot authentication and pop3/imap server
#

[INCLUDES]

before = common.conf

[Definition]

_auth_worker = (?:dovecot: )?auth(?:-worker)?
_daemon = (?:dovecot(?:-auth)?|auth)

__prefregex = ^%(__prefix_line)s(?:%(_auth_worker)s(?:\([^\)]+\))?: )?(?:%(__pam_auth)s(?:\(dovecot:auth\))?: |(?:pop3|imap)-login: )?(?:Info: )?

failregex = ^%(__prefregex)sauthentication failure; logname=\S* uid=\S* euid=\S* tty=dovecot ruser=\S* rhost=<HOST>(?:\s+user=\S*)?\s*$
            ^%(__prefregex)s(?:Aborted login|Disconnected)(?::(?: [^ \(]+)+)? \((?:auth failed, \d+ attempts(?: in \d+ secs)?|tried to use (?:disabled|disallowed) \S+ auth)\):(?: user=<[^>]*>,)?(?: method=\S+,)? rip=<HOST>(?:[^>]*(?:, session=<\S+>)?)\s*$
            ^%(__prefregex)spam\(\S+,<HOST>\): pam_authenticate\(\) failed: (?:User not known to the underlying authentication module: \d+ Time\(s\)|Authentication failure \(password mismatch\?\))\s*$
            ^%(__prefregex)s[a-z\-]{3,15}\(\S*,<HOST>(?:,\S*)?\): (?:unknown user|invalid credentials)\s*$

ignoreregex = 

[Init]

journalmatch = _SYSTEMD_UNIT=dovecot.service

# DEV Notes:
# * the first regex is essentially a copy of pam-generic.conf
# * Probably doesn't do dovecot sql/ldap backends properly (resolved in edit 21/03/2016)
# * Removed the 'no auth attempts' log lines from the matches because produces
#    lots of false positives on misconfigured MTAs making regexp unusable
#
# Author: Martin Waschbuesch
#         Daniel Black (rewrote with begin and end anchors)
#         Martin O'Neal (added LDAP authentication failure regex)
#         Sergey G. Brester aka sebres (reviewed, optimized, IPv6-compatibility)