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About Fail2Ban

Fail2Ban scans log files like /var/log/pwdfail and bans IP addresses that make too many password failures. 

It updates firewall rules to reject the IP address.

These rules can be defined by the user.

Fail2Ban can read multiple log files such as sshd or Apache Web server.

Installation

We install fail2ban package

sudo apt install fail2ban

Fail2ban configuration

The base configuration file of Fail2Ban is located at /etc/fail2ban/fail2ban.conf, and the jail using /etc/fail2ban/jail.conf.

Beneath an example of fail2ban.conf.

# Fail2Ban main configuration file
#
# Comments: use '#' for comment lines and ';' (following a space) for inline comments
#
# Changes:  in most of the cases you should not modify this
#           file, but provide customizations in fail2ban.local file, e.g.:
#
# [Definition]
# loglevel = DEBUG
#

[Definition]

# Option: loglevel
# Notes.: Set the log level output.
#         CRITICAL
#         ERROR
#         WARNING
#         NOTICE
#         INFO
#         DEBUG
# Values: [ LEVEL ]  Default: ERROR
#
loglevel = INFO

# Option: logtarget
# Notes.: Set the log target. This could be a file, SYSLOG, STDERR or STDOUT.
#         Only one log target can be specified.
#         If you change logtarget from the default value and you are
#         using logrotate -- also adjust or disable rotation in the
#         corresponding configuration file
#         (e.g. /etc/logrotate.d/fail2ban on Debian systems)
# Values: [ STDOUT | STDERR | SYSLOG | FILE ]  Default: STDERR
#
logtarget = /var/log/fail2ban.log

# Option: syslogsocket
# Notes: Set the syslog socket file. Only used when logtarget is SYSLOG
#        auto uses platform.system() to determine predefined paths
# Values: [ auto | FILE ]  Default: auto
syslogsocket = auto

# Option: socket
# Notes.: Set the socket file. This is used to communicate with the daemon. Do
#         not remove this file when Fail2ban runs. It will not be possible to
#         communicate with the server afterwards.
# Values: [ FILE ]  Default: /var/run/fail2ban/fail2ban.sock
#
socket = /var/run/fail2ban/fail2ban.sock

# Option: pidfile
# Notes.: Set the PID file. This is used to store the process ID of the
#         fail2ban server.
# Values: [ FILE ]  Default: /var/run/fail2ban/fail2ban.pid
#
pidfile = /var/run/fail2ban/fail2ban.pid

# Options: dbfile
# Notes.: Set the file for the fail2ban persistent data to be stored.
#         A value of ":memory:" means database is only stored in memory
#         and data is lost when fail2ban is stopped.
#         A value of "None" disables the database.
# Values: [ None :memory: FILE ] Default: /var/lib/fail2ban/fail2ban.sqlite3
dbfile = /var/lib/fail2ban/fail2ban.sqlite3

# Options: dbpurgeage
# Notes.: Sets age at which bans should be purged from the database
# Values: [ SECONDS ] Default: 86400 (24hours)
dbpurgeage = 172800 #2 days

Exemple of jail.conf.

# Fail2Ban configuration file.
#
# This file was composed for Debian systems from the original one
# provided now under /usr/share/doc/fail2ban/examples/jail.conf
# for additional examples.
#
# Comments: use '#' for comment lines and ';' for inline comments
#
# To avoid merges during upgrades DO NOT MODIFY THIS FILE
# and rather provide your changes in /etc/fail2ban/jail.local
#

# The DEFAULT allows a global definition of the options. They can be overridden
# in each jail afterwards.

[DEFAULT]

# "ignoreip" can be an IP address, a CIDR mask or a DNS host. Fail2ban will not
# ban a host which matches an address in this list. Several addresses can be
# defined using space separator.
ignoreip = 127.0.0.1/8
# External command that will take an tagged arguments to ignore, e.g. <ip>,
# and return true if the IP is to be ignored. False otherwise.
#
# ignorecommand = /path/to/command <ip>
ignorecommand =

# "bantime" is the number of seconds that a host is banned.
bantime  = 172800 #2 days

# A host is banned if it has generated "maxretry" during the last "findtime"
# seconds.
findtime = 1800 #30 minutes
maxretry = 3

# "backend" specifies the backend used to get files modification.
# Available options are "pyinotify", "gamin", "polling" and "auto".
# This option can be overridden in each jail as well.
#
# pyinotify: requires pyinotify (a file alteration monitor) to be installed.
#            If pyinotify is not installed, Fail2ban will use auto.
# gamin:     requires Gamin (a file alteration monitor) to be installed.
#            If Gamin is not installed, Fail2ban will use auto.
# polling:   uses a polling algorithm which does not require external libraries.
# auto:      will try to use the following backends, in order:
#            pyinotify, gamin, polling.
backend = auto

# "usedns" specifies if jails should trust hostnames in logs,
#   warn when reverse DNS lookups are performed, or ignore all hostnames in logs
#
# yes:   if a hostname is encountered, a reverse DNS lookup will be performed.
# warn:  if a hostname is encountered, a reverse DNS lookup will be performed,
#        but it will be logged as a warning.
# no:    if a hostname is encountered, will not be used for banning,
#        but it will be logged as info.
usedns = warn

#
# Destination email address used solely for the interpolations in
# jail.{conf,local} configuration files.
destemail = root@localhost

#
# Name of the sender for mta actions
sendername = Fail2Ban

# Email address of the sender
sender = fail2ban@localhost

#
# ACTIONS
#

# Default banning action (e.g. iptables, iptables-new,
# iptables-multiport, shorewall, etc) It is used to define
# action_* variables. Can be overridden globally or per
# section within jail.local file
banaction = iptables-allports

# email action. Since 0.8.1 upstream fail2ban uses sendmail
# MTA for the mailing. Change mta configuration parameter to mail
# if you want to revert to conventional 'mail'.
mta = sendmail

# Default protocol
protocol = tcp

# Specify chain where jumps would need to be added in iptables-* actions
chain = INPUT

#
# Action shortcuts. To be used to define action parameter

# The simplest action to take: ban only
action_ = %(banaction)s[name=%(__name__)s, port="%(port)s", protocol="%(protocol)s", chain="%(chain)s"]

# ban & send an e-mail with whois report to the destemail.
action_mw = %(banaction)s[name=%(__name__)s, port="%(port)s", protocol="%(protocol)s", chain="%(chain)s"]
              %(mta)s-whois[name=%(__name__)s, dest="%(destemail)s", protocol="%(protocol)s", chain="%(chain)s", sendername="%(sendername)s"]

# ban & send an e-mail with whois report and relevant log lines
# to the destemail.
action_mwl = %(banaction)s[name=%(__name__)s, port="%(port)s", protocol="%(protocol)s", chain="%(chain)s"]
               %(mta)s-whois-lines[name=%(__name__)s, dest="%(destemail)s", logpath=%(logpath)s, chain="%(chain)s", sendername="%(sendername)s"]

# Choose default action.  To change, just override value of 'action' with the
# interpolation to the chosen action shortcut (e.g.  action_mw, action_mwl, etc) in jail.local
# globally (section [DEFAULT]) or per specific section
action = %(action_)s

#
# JAILS
#

# Next jails corresponds to the standard configuration in Fail2ban 0.6 which
# was shipped in Debian. Enable any defined here jail by including
#
# [SECTION_NAME]
# enabled = true

#
# in /etc/fail2ban/jail.local.
#
# Optionally you may override any other parameter (e.g. banaction,
# action, port, logpath, etc) in that section within jail.local

[ssh]

enabled  = true
port     = 22
filter   = sshd
logpath  = /var/log/auth.log
maxretry = 3

[dropbear]

enabled  = false
port     = ssh
filter   = dropbear
logpath  = /var/log/auth.log
maxretry = 6

# Generic filter for pam. Has to be used with action which bans all ports
# such as iptables-allports, shorewall
[pam-generic]

enabled  = false
# pam-generic filter can be customized to monitor specific subset of 'tty's
filter   = pam-generic
# port actually must be irrelevant but lets leave it all for some possible uses
banaction = iptables-allports
port     = anyport
logpath  = /var/log/auth.log
maxretry = 3

[xinetd-fail]

enabled   = false
filter    = xinetd-fail
port      = all
banaction = iptables-multiport-log
logpath   = /var/log/daemon.log
maxretry  = 3


[ssh-ddos]

enabled  = true
port     = ssh
filter   = sshd-ddos
logpath  = /var/log/auth.log
maxretry = 3


# Here we use blackhole routes for not requiring any additional kernel support
# to store large volumes of banned IPs

[ssh-route]

enabled = false
filter = sshd
action = route
logpath = /var/log/sshd.log
maxretry = 6

# Here we use a combination of Netfilter/Iptables and IPsets
# for storing large volumes of banned IPs
#
# IPset comes in two versions. See ipset -V for which one to use
# requires the ipset package and kernel support.
[ssh-iptables-ipset4]

enabled  = false
port     = ssh
filter   = sshd
banaction = iptables-ipset-proto4
logpath  = /var/log/sshd.log
maxretry = 6

[ssh-iptables-ipset6]

enabled  = false
port     = ssh
filter   = sshd
banaction = iptables-ipset-proto6
logpath  = /var/log/sshd.log
maxretry = 6


#
# HTTP servers
#

[apache]

enabled  = false
port     = http,https
filter   = apache-auth
logpath  = /var/log/apache*/*error.log
maxretry = 6

# default action is now multiport, so apache-multiport jail was left
# for compatibility with previous (<0.7.6-2) releases
[apache-multiport]

enabled   = false
port      = http,https
filter    = apache-auth
logpath   = /var/log/apache*/*error.log
maxretry  = 6

[apache-noscript]

enabled  = false
port     = http,https
filter   = apache-noscript
logpath  = /var/log/apache*/*error.log
maxretry = 6

[apache-overflows]

enabled  = false
port     = http,https
filter   = apache-overflows
logpath  = /var/log/apache*/*error.log
maxretry = 2

[apache-modsecurity]

enabled  = false
filter   = apache-modsecurity
port     = http,https
logpath  = /var/log/apache*/*error.log
maxretry = 2

[apache-nohome]

enabled  = false
filter   = apache-nohome
port     = http,https
logpath  = /var/log/apache*/*error.log
maxretry = 2

# Ban attackers that try to use PHP's URL-fopen() functionality
# through GET/POST variables. - Experimental, with more than a year
# of usage in production environments.

[php-url-fopen]

enabled = false
port    = http,https
filter  = php-url-fopen
logpath = /var/www/*/logs/access_log

# A simple PHP-fastcgi jail which works with lighttpd.
# If you run a lighttpd server, then you probably will
# find these kinds of messages in your error_log:
#   ALERT – tried to register forbidden variable ‘GLOBALS’
#   through GET variables (attacker '1.2.3.4', file '/var/www/default/htdocs/index.php')

[lighttpd-fastcgi]

enabled = false
port    = http,https
filter  = lighttpd-fastcgi
logpath = /var/log/lighttpd/error.log

# Same as above for mod_auth
# It catches wrong authentifications

[lighttpd-auth]

enabled = false
port    = http,https
filter  = suhosin
logpath = /var/log/lighttpd/error.log

[nginx-http-auth]

enabled = true
filter  = nginx-http-auth
port    = http,https
logpath = /var/log/nginx/error.log


[nginx-noscript]
enabled = false
action = iptables-multiport[name=NoScript, port="http,https"]
filter = nginx-noscript
logpath = /var/log/nginx/access.log
maxretry = 3


[nginx-badbots]
enabled  = true
filter = apache-badbots
action = iptables-multiport[name=BadBots, port="http,https"]
logpath = /var/log/nginx/access.log
maxretry = 3


[apache-w00tw00t]
enabled = true
filter = apache-w00tw00t
action = iptables[name=Apache-w00tw00t,port=80,protocol=tcp]
logpath =  /var/log/nginx/access.log
maxretry = 1
# Monitor roundcube server

[roundcube-auth]

enabled  = false
filter   = roundcube-auth
port     = http,https
logpath  = /var/log/roundcube/userlogins


[sogo-auth]

enabled  = false
filter   = sogo-auth
port     = http, https
# without proxy this would be:
# port    = 20000
logpath  = /var/log/sogo/sogo.log


#
# FTP servers
#

[vsftpd]

enabled  = false
port     = ftp,ftp-data,ftps,ftps-data
filter   = vsftpd
logpath  = /var/log/vsftpd.log
# or overwrite it in jails.local to be
# logpath = /var/log/auth.log
# if you want to rely on PAM failed login attempts
# vsftpd's failregex should match both of those formats
maxretry = 6


[proftpd]

enabled  = false
port     = ftp,ftp-data,ftps,ftps-data
filter   = proftpd
logpath  = /var/log/proftpd/proftpd.log
maxretry = 6


[pure-ftpd]

enabled  = false
port     = ftp,ftp-data,ftps,ftps-data
filter   = pure-ftpd
logpath  = /var/log/syslog
maxretry = 6


[wuftpd]

enabled  = false
port     = ftp,ftp-data,ftps,ftps-data
filter   = wuftpd
logpath  = /var/log/syslog
maxretry = 6


#
# Mail servers
#

[postfix]

enabled  = true
port     = smtp,ssmtp,submission
filter   = postfix
logpath  = /var/log/mail.log
maxretry = 1
findtime = 86400 #1 days
bantime  = -1 #permanent ban

[couriersmtp]

enabled  = false
port     = smtp,ssmtp,submission
filter   = couriersmtp
logpath  = /var/log/mail.log


#
# Mail servers authenticators: might be used for smtp,ftp,imap servers, so
# all relevant ports get banned
#

[courierauth]

enabled  = false
port     = smtp,ssmtp,submission,imap2,imap3,imaps,pop3,pop3s
filter   = courierlogin
logpath  = /var/log/mail.log


[sasl]

enabled  = false
port     = smtp,ssmtp,submission,imap2,imap3,imaps,pop3,pop3s
filter   = postfix-sasl
# You might consider monitoring /var/log/mail.warn instead if you are
# running postfix since it would provide the same log lines at the
# "warn" level but overall at the smaller filesize.
logpath  = /var/log/mail.log

[dovecot]

enabled = false
port    = smtp,ssmtp,submission,imap2,imap3,imaps,pop3,pop3s
filter  = dovecot
logpath = /var/log/mail.log

# To log wrong MySQL access attempts add to /etc/my.cnf:
# log-error=/var/log/mysqld.log
# log-warning = 2
[mysqld-auth]

enabled  = true
filter   = mysqld-auth
port     = 3306
logpath  = /var/log/syslog
findtime = 604800
bantime = 29030400
maxretry = 2

# DNS Servers


# These jails block attacks against named (bind9). By default, logging is off
# with bind9 installation. You will need something like this:
#
# logging {
#     channel security_file {
#         file "/var/log/named/security.log" versions 3 size 30m;
#         severity dynamic;
#         print-time yes;
#     };
#     category security {
#         security_file;
#     };
# };
#
# in your named.conf to provide proper logging

# !!! WARNING !!!
#   Since UDP is connection-less protocol, spoofing of IP and imitation
#   of illegal actions is way too simple.  Thus enabling of this filter
#   might provide an easy way for implementing a DoS against a chosen
#   victim. See
#    http://nion.modprobe.de/blog/archives/690-fail2ban-+-dns-fail.html
#   Please DO NOT USE this jail unless you know what you are doing.
#[named-refused-udp]
#
#enabled  = false
#port     = domain,953
#protocol = udp
#filter   = named-refused
#logpath  = /var/log/named/security.log

[named-refused-tcp]

enabled  = false
port     = domain,953
protocol = tcp
filter   = named-refused
logpath  = /var/log/named/security.log

[freeswitch]

enabled  = false
filter   = freeswitch
logpath  = /var/log/freeswitch.log
maxretry = 10
action   = iptables-multiport[name=freeswitch-tcp, port="5060,5061,5080,5081", protocol=tcp]
           iptables-multiport[name=freeswitch-udp, port="5060,5061,5080,5081", protocol=udp]

[ejabberd-auth]

enabled  = false
filter   = ejabberd-auth
port     = xmpp-client
protocol = tcp
logpath  = /var/log/ejabberd/ejabberd.log


# Multiple jails, 1 per protocol, are necessary ATM:
# see https://github.com/fail2ban/fail2ban/issues/37
[asterisk-tcp]

enabled  = false
filter   = asterisk
port     = 5060,5061
protocol = tcp
logpath  = /var/log/asterisk/messages

[asterisk-udp]

enabled  = false
filter   = asterisk
port     = 5060,5061
protocol = udp
logpath  = /var/log/asterisk/messages


# Jail for more extended banning of persistent abusers
# !!! WARNING !!!
#   Make sure that your loglevel specified in fail2ban.conf/.local
#   is not at DEBUG level -- which might then cause fail2ban to fall into
#   an infinite loop constantly feeding itself with non-informative lines
[recidive]

enabled  = false
filter   = recidive
logpath  = /var/log/fail2ban.log
action   = iptables-allports[name=recidive]
           sendmail-whois-lines[name=recidive, logpath=/var/log/fail2ban.log]
bantime  = 604800  ; 1 week
findtime = 86400   ; 1 day
maxretry = 5

# See the IMPORTANT note in action.d/blocklist_de.conf for when to
# use this action
#
# Report block via blocklist.de fail2ban reporting service API
# See action.d/blocklist_de.conf for more information
[ssh-blocklist]

enabled  = false
filter   = sshd
action   = iptables[name=SSH, port=ssh, protocol=tcp]
           sendmail-whois[name=SSH, dest="%(destemail)s", sender="%(sender)s", sendername="%(sendername)s"]
           blocklist_de[email="%(sender)s", apikey="xxxxxx", service="%(filter)s"]
logpath  = /var/log/sshd.log
maxretry = 20


# consider low maxretry and a long bantime
# nobody except your own Nagios server should ever probe nrpe
[nagios]
enabled  = false
filter   = nagios
action   = iptables[name=Nagios, port=5666, protocol=tcp]
           sendmail-whois[name=Nagios, dest="%(destemail)s", sender="%(sender)s", sendername="%(sendername)s"]
logpath  = /var/log/messages     ; nrpe.cfg may define a different log_facility
maxretry = 3

It is possible to use specific findtime and bantime for each jail we create.

Example for nginx bad bot.

[nginx-badbots]
enabled  = true
filter = apache-badbots
action = iptables-multiport[name=BadBots, port="http,https"]
logpath = /var/log/nginx/access.log
maxretry = 3
findtime = 604800  #1 week
bantime = 29030400 #1 year

Filter definition

The rules filter for our jail is defined in /etc/fail2ban/filter.d.

Exemple for nginx bad bot.

# Fail2Ban configuration file
#
# Regexp to catch known spambots and software alike. Please verify
# that it is your intent to block IPs which were driven by
# above mentioned bots.

[Definition]

badbotscustom = EmailCollector|WebEMailExtrac|TrackBack/1\.02|sogou|music|spider|zgrab/0.x|MJ12bot/v1.4.4|MJ12bot/v1.4.5|MJ12bot/v1.2.1|MJ12bot/v1.4.2|MJ12bot/v1.4.3|MJ12bot/v1.3.3|MJ12bot/ |WEBDAV |Xenu Link Sleuth/1.3.8
badbots = Atomic_Email_Hunter/4\.0|atSpider/1\.0|autoemailspider|bwh3_user_agent|China Local Browse 2\.6|ContactBot/0\.2|ContentSmartz|DataCha0s/2\.0|DBrowse 1\.4b|DBrowse 1\.4d|Demo Bot DOT 16b|Demo Bot Z 16b|DSurf15a 01|DSurf15a 71|DSurf15a 81|DSurf15a VA|EBrowse 1\.4b|Educate Search VxB|EmailSiphon|EmailSpider|EmailWolf 1\.00|ESurf15a 15|ExtractorPro|Franklin Locator 1\.8|FSurf15a 01|Full Web Bot 0416B|Full Web Bot 0516B|Full Web Bot 2816B|Guestbook Auto Submitter|Industry Program 1\.0\.x|ISC Systems iRc Search 2\.1|IUPUI Research Bot v 1\.9a|LARBIN-EXPERIMENTAL \(efp@gmx\.net\)|LetsCrawl\.com/1\.0 +http\://letscrawl\.com/|Lincoln State Web Browser|LMQueueBot/0\.2|LWP\:\:Simple/5\.803|Mac Finder 1\.0\.xx|MFC Foundation Class Library 4\.0|Microsoft URL Control - 6\.00\.8xxx|Missauga Locate 1\.0\.0|Missigua Locator 1\.9|Missouri College Browse|Mizzu Labs 2\.2|Mo College 1\.9|MVAClient|Mozilla/2\.0 \(compatible; NEWT ActiveX; Win32\)|Mozilla/3\.0 \(compatible; Indy Library\)|Mozilla/3\.0 \(compatible; scan4mail \(advanced version\) http\://www\.peterspages\.net/?scan4mail\)|Mozilla/4\.0 \(compatible; Advanced Email Extractor v2\.xx\)|Mozilla/4\.0 \(compatible; Iplexx Spider/1\.0 http\://www\.iplexx\.at\)|Mozilla/4\.0 \(compatible; MSIE 5\.0; Windows NT; DigExt; DTS Agent|Mozilla/4\.0 efp@gmx\.net|Mozilla/5\.0 \(Version\: xxxx Type\:xx\)|NameOfAgent \(CMS Spider\)|NASA Search 1\.0|Nsauditor/1\.x|PBrowse 1\.4b|PEval 1\.4b|Poirot|Port Huron Labs|Production Bot 0116B|Production Bot 2016B|Production Bot DOT 3016B|Program Shareware 1\.0\.2|PSurf15a 11|PSurf15a 51|PSurf15a VA|psycheclone|RSurf15a 41|RSurf15a 51|RSurf15a 81|searchbot admin@google\.com|ShablastBot 1\.0|snap\.com beta crawler v0|Snapbot/1\.0|Snapbot/1\.0 \(Snap Shots&#44; +http\://www\.snap\.com\)|sogou develop spider|Sogou Orion spider/3\.0\(+http\://www\.sogou\.com/docs/help/webmasters\.htm#07\)|sogou spider|Sogou web spider/3\.0\(+http\://www\.sogou\.com/docs/help/webmasters\.htm#07\)|sohu agent|SSurf15a 11 |TSurf15a 11|Under the Rainbow 2\.2|User-Agent\: Mozilla/4\.0 \(compatible; MSIE 6\.0; Windows NT 5\.1\)|VadixBot|WebVulnCrawl\.unknown/1\.0 libwww-perl/5\.803|Wells Search II|WEP Search 00

failregex = ^<HOST> -.*"(GET|POST|PROFIND).*HTTP.*"(?:%(badbots)s|%(badbotscustom)s)"$

# try to access to directory
     ^<HOST> .*?"GET .*dbadmin.* 404
     ^<HOST> .*?"GET .*myadmin.* 404
     ^<HOST> .*?"GET .*MyAdmin.* 404
     ^<HOST> .*?"GET .*mysql.* 404
     ^<HOST> .*?"GET .*websql.* 404
     ^<HOST> .*?"GET .*webdb.* 404
     ^<HOST> .*?"GET .*webadmin.* 404
     ^<HOST> .*?"GET .*phppath.* 404
     ^<HOST> .*?"GET .*databaseadmin.* 404
     ^<HOST> .*?"GET .*mysqlmanager.* 404
     ^<HOST> .*?"GET .*phpMyAdmin.* 404
     ^<HOST> .*?"GET .*xampp.* 404
     ^<HOST> .*?"GET .*sqlmanager.* 404
     ^<HOST> .*?"GET .*wp-content.* 404
     ^<HOST> .*?"GET .*wp-login.* 404
     ^<HOST> .*?"GET .*typo3.* 404
     ^<HOST> .*?"HEAD .*manager.* 404
     ^<HOST> .*?"GET .*manager.* 404
     ^<HOST> .*?"HEAD .*blackcat.* 404
     ^<HOST> .*?"HEAD .*sprawdza.php.* 404
     ^<HOST> .*?"GET .*HNAP1.* 404
     ^<HOST> .*?"GET .*vtigercrm.* 404
     ^<HOST> .*?"GET .*cgi-bin* 404
     ^<HOST> .*?"GET .*webdav.* 404
     ^<HOST> .*?"GET .*web-console.* 404
     ^<HOST> .*?"GET .*manager.* 404
     ^<HOST> .*?"GET .*azenv* 404
ignoreregex =

# DEV Notes:
# List of bad bots fetched from http://www.user-agents.org
# Generated on Thu Nov  7 14:23:35 PST 2013 by files/gen_badbots.
#
# Author: Yaroslav Halchenko

An example of a ban when a bot try to use our server SMTP as relay to send their spams

# Fail2Ban filter for selected Postfix SMTP rejections
#
#

[INCLUDES]

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

[Definition]

_daemon = postfix(-\w+)?/(?:submission/|smtps/)?smtp[ds]

failregex = ^%(__prefix_line)sNOQUEUE: reject: RCPT from \S+\[<HOST>\]: 554 5\.7\.1 .*$
            ^%(__prefix_line)sNOQUEUE: reject: RCPT from \S+\[<HOST>\]: 450 4\.7\.1 Client host rejected: cannot find your hostname, (\[\S*\]); from=<\S*> to=<\S+> proto=ESMTP helo=<\S*>$
            ^%(__prefix_line)sNOQUEUE: reject: RCPT from \S+\[<HOST>\]: 450 4\.7\.1 : Helo command rejected: Host not found; from=<> to=<> proto=ESMTP helo= *$
            ^%(__prefix_line)sNOQUEUE: reject: EHLO from \S+\[<HOST>\]: 504 5\.5\.2 <\S+>: Helo command rejected: need fully-qualified hostname;
            ^%(__prefix_line)sNOQUEUE: reject: VRFY from \S+\[<HOST>\]: 550 5\.1\.1 .*$
            ^%(__prefix_line)sNOQUEUE: reject: RCPT from \S+\[<HOST>\]: 450 4\.1\.8 <\S*>: Sender address rejected: Domain not found; from=<\S*> to=<\S+> proto=ESMTP helo=<\S*>$
            ^%(__prefix_line)simproper command pipelining after \S+ from [^[]*\[<HOST>\]:?$
            ^%(__prefix_line)slost connection after \S+ from \S+\[<HOST>\]$
            ^%(__prefix_line)sNOQUEUE: reject: RCPT from \S+\[<HOST>\]: 454 4\.7\.1 .*$

ignoreregex =


[Init]

journalmatch = _SYSTEMD_UNIT=postfix.service

# Author: Cyril Jaquier

When you have finish to configure, you must restart fail2ban service to apply your modifications.

systemctl restart fail2ban.service

Troubleshooting

If fail2ban is to restrictive you can ban your IP by error.

You can remove your IP from the banlist.

fail2ban-client set $jail unbanip $IP

If you want to test your regular expression after an edition of your filter config file you can use =>

fail2ban-regex $logfile /etc/fail2ban/filter.d/$filter.conf