fail2ban/config/filter.d/znc-adminlog.conf

# Fail2Ban filter for ZNC (requires adminlog module)
#
# to use this module, enable the adminlog module from within ZNC and point
# logpath to its logfile (e.g. /var/lib/znc/moddata/adminlog/znc.log).

[DEFAULT]

logtype = file

[Definition]

_daemon = znc

# Prefix for different logtype (file, journal):
#
__prefix_file = (?:\[\]\s+)?
__prefix_short = (?:\S+\s+%(_daemon)s\[\d+\]:)\s+
__prefix_journal = %(__prefix_short)s

__prefix_line = <__prefix_<logtype>>

failregex = ^%(__prefix_line)s\[[^]]+\] failed to login from <ADDR>

ignoreregex = 

journalmatch = _SYSTEMD_UNIT=znc.service + _COMM=znc

# DEV Notes:
# Log format is: [<DATE+TIME>] [<USERNAME>] <ACTION> from <ADDR>
# [2018-10-27 01:40:17] [girst] connected to ZNC from 1.2.3.4
# [2018-10-27 01:40:21] [girst] disconnected from ZNC from 1.2.3.4
# [2018-10-27 01:40:55] [girst] failed to login from 1.2.3.4
#
# Author: Tobias Girstmair (//gir.st/)