fail2ban/config/filter.d/roundcube-auth.conf

# Fail2Ban configuration file for roundcube web server
#
#
#

[INCLUDES]

before = common.conf

[Definition]

failregex = ^\s*(\[(\s[+-][0-9]{4})?\])?(%(__hostname)s roundcube: IMAP Error)?: (FAILED login|Login failed) for .*? from <HOST>(\. .* in .*?/rcube_imap\.php on line \d+ \(\S+ \S+\))?$

ignoreregex = 
# DEV Notes:
#
# Source: https://github.com/roundcube/roundcubemail/blob/master/program/lib/Roundcube/rcube_imap.php#L180
#
# Part after <HOST> comes straight from IMAP server up until the " in ....."
# Earlier versions didn't log the IMAP response hence optional.
#
# DoS resistance:
#
# Assume that the user can inject "from <HOST>" into the imap response
# somehow. Write test cases around this to ensure that the combination of
# arbitrary user input and IMAP response doesn't inject the wrong IP for
# fail2ban
#
# Author: Teodor Micu & Yaroslav Halchenko & terence namusonge & Daniel Black