fail2ban/config/filter.d/exim.conf

# Fail2Ban filter for exim
#
# This includes the rejection messages of exim. For spam and filter
# related bans use the exim-spam.conf
#


[INCLUDES]

# Read common prefixes. If any customizations available -- read them from
# exim-common.local
before = exim-common.conf

[Definition]

prefregex = ^%(__prefix_line)s<F-CONTENT>.+</F-CONTENT>$

failregex = ^%(host_info)s sender verify fail for <\S+>: (?:Unknown user|Unrouteable address|all relevant MX records point to non-existent hosts)\s*$
            ^\s?\w+ authenticator failed for%(host_info)s: 535 Incorrect authentication data(?: \(set_id=.*\)|: \d+ Time\(s\))?\s*$
            ^%(host_info)s rejected RCPT [^@]+@\S+: (?:relay not permitted|Sender verify failed|Unknown user|Unrouteable address)\s*$
            ^\s?SMTP protocol synchronization error \([^)]*\): rejected (?:connection from|"\S+")%(host_info)s (?:next )?input=".*"\s*$
            ^\s?SMTP call from%(host_info)s dropped: too many (?:(?:nonmail|unrecognized) commands|syntax or protocol errors)
            ^\s?SMTP protocol error in "[^"]+(?:"+[^"]*(?="))*?"%(host_info)s AUTH command used when not advertised\s*$
            ^\s?no MAIL in SMTP connection from%(host_info)s
            ^\s?(?:[\w\-]+ )?SMTP connection from%(host_info)s closed by DROP in ACL\s*$
            <mdre-<mode>>

mdre-aggressive = ^\s?no host name found for IP address <ADDR>$
                  ^\s?no IP address found for host \S+ \(during SMTP connection from%(host_info)s\)$

mdre-normal = 

# Parameter `mode` - `normal` or `aggressive`.
# Aggressive mode can be used to match flood and ddos-similar log-entries like:
#   'no host found for IP', 'no IP found for host'.
# Note this is not an authentication failures, so it may produce lots of false 
# positives on misconfigured MTAs.
# Ex.:
#   filter = exim[mode=aggressive]
mode = normal

ignoreregex = 

# DEV Notes
# -----------
# The %(host_info) definition contains a <ADDR> match. No space before. See exim-common.conf
#
# SMTP protocol synchronization error \([^)]*\)  <- This needs to be non-greedy
# to void capture beyond ")" to avoid a DoS Injection vulnerability as input= is
# user injectable data.