Fail2Ban - Install and configure

As the description says:

Fail2ban scans log files and bans IPs that show the malicious signs (too many password failures, seeking for exploits, etc). Generally Fail2Ban is then used to update firewall rules to reject the IP addresses for a specified amount of time.

Installation

Requirements

• Python >= 2.4
• Optional:
  • IPTables
  • Shorewall
  • TCP-Wrappers
  • Mail server (smail)

Debian

For Debian based systems is as easy as:

sudo apt install fail2ban -y

Gentoo

emerge fail2ban

Fedora

yum install fail2ban

There is a bug in version (0.8.4-27) which will prevent jails from starting.

In the jail.conf file, change: backend = auto to backend = gamin, then yum install gamin.

Fail2Ban service

By default, as we can see from installation, it creates a service and enables it, so that it will launch on boot:

...
Created symlink /etc/systemd/system/multi-user.target.wants/fail2ban.service → /lib/systemd/system/fail2ban.service.
...

n0nuser@n0nuser:~$ systemctl status fail2ban.service 
● fail2ban.service - Fail2Ban Service
     Loaded: loaded (/lib/systemd/system/fail2ban.service; enabled; vendor pres>
     Active: active (running) since Sat 2021-03-06 17:40:44 CET; 21s ago
       Docs: man:fail2ban(1)
   Main PID: 17722 (f2b/server)
      Tasks: 5 (limit: 9335)
     Memory: 14.3M
     CGroup: /system.slice/fail2ban.service
             └─17722 /usr/bin/python3 /usr/bin/fail2ban-server -xf start

mar 06 17:40:44 n0nuser systemd[1]: Starting Fail2Ban Service...
mar 06 17:40:44 n0nuser systemd[1]: Started Fail2Ban Service.
mar 06 17:40:45 n0nuser fail2ban-server[17722]: Server ready

We can disable (in case of needed) it with:

sudo systemctl disable fail2ban.service

Configuration

Fail2Ban is pretty much configured by default. It has 2 files, the general configuration file (/etc/fail2ban/fail2ban.conf), and the specific configuration file (/etc/fail2ban/jail.conf).

It’s not advised to modify these files. Instead is better to create one called jail.local, or fail2ban.local in the same directory.

Default general configuration file:

# 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.:
#
# [DEFAULT]
# loglevel = DEBUG
#

[DEFAULT]

# 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 | SYSOUT | 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 = 1d

# Options: dbmaxmatches
# Notes.: Number of matches stored in database per ticket (resolvable via 
#         tags <ipmatches>/<ipjailmatches> in actions)
# Values: [ INT ] Default: 10
dbmaxmatches = 10

[Definition]


[Thread]

# Options: stacksize
# Notes.: Specifies the stack size (in KiB) to be used for subsequently created threads,
#         and must be 0 or a positive integer value of at least 32.
# Values: [ SIZE ] Default: 0 (use platform or configured default)
#stacksize = 0

Default specific configuration file:

#
# WARNING: heavily refactored in 0.9.0 release.  Please review and
#          customize settings for your setup.
#
# Changes:  in most of the cases you should not modify this
#           file, but provide customizations in jail.local file,
#           or separate .conf files under jail.d/ directory, e.g.:
#
# HOW TO ACTIVATE JAILS:
#
# YOU SHOULD NOT MODIFY THIS FILE.
#
# It will probably be overwritten or improved in a distribution update.
#
# Provide customizations in a jail.local file or a jail.d/customisation.local.
# For example to change the default bantime for all jails and to enable the
# ssh-iptables jail the following (uncommented) would appear in the .local file.
# See man 5 jail.conf for details.
#
# [DEFAULT]
# bantime = 1h
#
# [sshd]
# enabled = true
#
# See jail.conf(5) man page for more information



# Comments: use '#' for comment lines and ';' (following a space) for inline comments


[INCLUDES]

#before = paths-distro.conf
before = paths-debian.conf

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

[DEFAULT]

#
# MISCELLANEOUS OPTIONS
#

# "bantime.increment" allows to use database for searching of previously banned ip's to increase a 
# default ban time using special formula, default it is banTime * 1, 2, 4, 8, 16, 32...
#bantime.increment = true

# "bantime.rndtime" is the max number of seconds using for mixing with random time 
# to prevent "clever" botnets calculate exact time IP can be unbanned again:
#bantime.rndtime = 

# "bantime.maxtime" is the max number of seconds using the ban time can reach (don't grows further)
#bantime.maxtime = 

# "bantime.factor" is a coefficient to calculate exponent growing of the formula or common multiplier,
# default value of factor is 1 and with default value of formula, the ban time 
# grows by 1, 2, 4, 8, 16 ...
#bantime.factor = 1

# "bantime.formula" used by default to calculate next value of ban time, default value bellow,
# the same ban time growing will be reached by multipliers 1, 2, 4, 8, 16, 32...
#bantime.formula = ban.Time * (1<<(ban.Count if ban.Count<20 else 20)) * banFactor
#
# more aggressive example of formula has the same values only for factor "2.0 / 2.885385" :
#bantime.formula = ban.Time * math.exp(float(ban.Count+1)*banFactor)/math.exp(1*banFactor)

# "bantime.multipliers" used to calculate next value of ban time instead of formula, coresponding 
# previously ban count and given "bantime.factor" (for multipliers default is 1);
# following example grows ban time by 1, 2, 4, 8, 16 ... and if last ban count greater as multipliers count, 
# always used last multiplier (64 in example), for factor '1' and original ban time 600 - 10.6 hours
#bantime.multipliers = 1 2 4 8 16 32 64
# following example can be used for small initial ban time (bantime=60) - it grows more aggressive at begin,
# for bantime=60 the multipliers are minutes and equal: 1 min, 5 min, 30 min, 1 hour, 5 hour, 12 hour, 1 day, 2 day
#bantime.multipliers = 1 5 30 60 300 720 1440 2880

# "bantime.overalljails" (if true) specifies the search of IP in the database will be executed 
# cross over all jails, if false (dafault), only current jail of the ban IP will be searched
#bantime.overalljails = false

# --------------------

# "ignoreself" specifies whether the local resp. own IP addresses should be ignored
# (default is true). Fail2ban will not ban a host which matches such addresses.
#ignoreself = true

# "ignoreip" can be a list of IP addresses, CIDR masks or DNS hosts. Fail2ban
# will not ban a host which matches an address in this list. Several addresses
# can be defined using space (and/or comma) separator.
#ignoreip = 127.0.0.1/8 ::1

# 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  = 10m

# A host is banned if it has generated "maxretry" during the last "findtime"
# seconds.
findtime  = 10m

# "maxretry" is the number of failures before a host get banned.
maxretry = 5

# "maxmatches" is the number of matches stored in ticket (resolvable via tag <matches> in actions).
maxmatches = %(maxretry)s

# "backend" specifies the backend used to get files modification.
# Available options are "pyinotify", "gamin", "polling", "systemd" 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.
# systemd:   uses systemd python library to access the systemd journal.
#              Specifying "logpath" is not valid for this backend.
#              See "journalmatch" in the jails associated filter config
# auto:      will try to use the following backends, in order:
#              pyinotify, gamin, polling.
#
# Note: if systemd backend is chosen as the default but you enable a jail
#       for which logs are present only in its own log files, specify some other
#       backend for that jail (e.g. polling) and provide empty value for
#       journalmatch. See https://github.com/fail2ban/fail2ban/issues/959#issuecomment-74901200
backend = auto

# "usedns" specifies if jails should trust hostnames in logs,
#   warn when DNS lookups are performed, or ignore all hostnames in logs
#
# yes:   if a hostname is encountered, a DNS lookup will be performed.
# warn:  if a hostname is encountered, a 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.
# raw:   use raw value (no hostname), allow use it for no-host filters/actions (example user)
usedns = warn

# "logencoding" specifies the encoding of the log files handled by the jail
#   This is used to decode the lines from the log file.
#   Typical examples:  "ascii", "utf-8"
#
#   auto:   will use the system locale setting
logencoding = auto

# "enabled" enables the jails.
#  By default all jails are disabled, and it should stay this way.
#  Enable only relevant to your setup jails in your .local or jail.d/*.conf
#
# true:  jail will be enabled and log files will get monitored for changes
# false: jail is not enabled
enabled = false


# "mode" defines the mode of the filter (see corresponding filter implementation for more info).
mode = normal

# "filter" defines the filter to use by the jail.
#  By default jails have names matching their filter name
#
filter = %(__name__)s[mode=%(mode)s]


#
# ACTIONS
#

# Some options used for actions

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

# Sender email address used solely for some actions
sender = root@<fq-hostname>

# E-mail action. Since 0.8.1 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 ban-actions expecting parameter chain
chain = <known/chain>

# Ports to be banned
# Usually should be overridden in a particular jail
port = 0:65535

# Format of user-agent https://tools.ietf.org/html/rfc7231#section-5.5.3
fail2ban_agent = Fail2Ban/%(fail2ban_version)s

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

# 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-multiport
banaction_allports = iptables-allports

# 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, sender="%(sender)s", dest="%(destemail)s", protocol="%(protocol)s", chain="%(chain)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, sender="%(sender)s", dest="%(destemail)s", logpath="%(logpath)s", chain="%(chain)s"]

# See the IMPORTANT note in action.d/xarf-login-attack for when to use this action
#
# ban & send a xarf e-mail to abuse contact of IP address and include relevant log lines
# to the destemail.
action_xarf = %(banaction)s[name=%(__name__)s, port="%(port)s", protocol="%(protocol)s", chain="%(chain)s"]
             xarf-login-attack[service=%(__name__)s, sender="%(sender)s", logpath="%(logpath)s", port="%(port)s"]

# ban IP on CloudFlare & send an e-mail with whois report and relevant log lines
# to the destemail.
action_cf_mwl = cloudflare[cfuser="%(cfemail)s", cftoken="%(cfapikey)s"]
                %(mta)s-whois-lines[name=%(__name__)s, sender="%(sender)s", dest="%(destemail)s", logpath="%(logpath)s", chain="%(chain)s"]

# Report block via blocklist.de fail2ban reporting service API
# 
# See the IMPORTANT note in action.d/blocklist_de.conf for when to use this action.
# Specify expected parameters in file action.d/blocklist_de.local or if the interpolation
# `action_blocklist_de` used for the action, set value of `blocklist_de_apikey`
# in your `jail.local` globally (section [DEFAULT]) or per specific jail section (resp. in 
# corresponding jail.d/my-jail.local file).
#
action_blocklist_de  = blocklist_de[email="%(sender)s", service=%(filter)s, apikey="%(blocklist_de_apikey)s", agent="%(fail2ban_agent)s"]

# Report ban via badips.com, and use as blacklist
#
# See BadIPsAction docstring in config/action.d/badips.py for
# documentation for this action.
#
# NOTE: This action relies on banaction being present on start and therefore
# should be last action defined for a jail.
#
action_badips = badips.py[category="%(__name__)s", banaction="%(banaction)s", agent="%(fail2ban_agent)s"]
#
# Report ban via badips.com (uses action.d/badips.conf for reporting only)
#
action_badips_report = badips[category="%(__name__)s", agent="%(fail2ban_agent)s"]

# Report ban via abuseipdb.com.
#
# See action.d/abuseipdb.conf for usage example and details.
#
action_abuseipdb = abuseipdb

# 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
#

#
# SSH servers
#

[sshd]

# To use more aggressive sshd modes set filter parameter "mode" in jail.local:
# normal (default), ddos, extra or aggressive (combines all).
# See "tests/files/logs/sshd" or "filter.d/sshd.conf" for usage example and details.
#mode   = normal
port    = ssh
logpath = %(sshd_log)s
backend = %(sshd_backend)s


[dropbear]

port     = ssh
logpath  = %(dropbear_log)s
backend  = %(dropbear_backend)s


[selinux-ssh]

port     = ssh
logpath  = %(auditd_log)s


#
# HTTP servers
#

[apache-auth]

port     = http,https
logpath  = %(apache_error_log)s


[apache-badbots]
# Ban hosts which agent identifies spammer robots crawling the web
# for email addresses. The mail outputs are buffered.
port     = http,https
logpath  = %(apache_access_log)s
bantime  = 48h
maxretry = 1


[apache-noscript]

port     = http,https
logpath  = %(apache_error_log)s


[apache-overflows]

port     = http,https
logpath  = %(apache_error_log)s
maxretry = 2


[apache-nohome]

port     = http,https
logpath  = %(apache_error_log)s
maxretry = 2


[apache-botsearch]

port     = http,https
logpath  = %(apache_error_log)s
maxretry = 2


[apache-fakegooglebot]

port     = http,https
logpath  = %(apache_access_log)s
maxretry = 1
ignorecommand = %(ignorecommands_dir)s/apache-fakegooglebot <ip>


[apache-modsecurity]

port     = http,https
logpath  = %(apache_error_log)s
maxretry = 2


[apache-shellshock]

port    = http,https
logpath = %(apache_error_log)s
maxretry = 1


[openhab-auth]

filter = openhab
action = iptables-allports[name=NoAuthFailures]
logpath = /opt/openhab/logs/request.log


[nginx-http-auth]

port    = http,https
logpath = %(nginx_error_log)s

# To use 'nginx-limit-req' jail you should have `ngx_http_limit_req_module` 
# and define `limit_req` and `limit_req_zone` as described in nginx documentation
# http://nginx.org/en/docs/http/ngx_http_limit_req_module.html
# or for example see in 'config/filter.d/nginx-limit-req.conf'
[nginx-limit-req]
port    = http,https
logpath = %(nginx_error_log)s

[nginx-botsearch]

port     = http,https
logpath  = %(nginx_error_log)s
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]

port    = http,https
logpath = %(nginx_access_log)s
          %(apache_access_log)s


[suhosin]

port    = http,https
logpath = %(suhosin_log)s


[lighttpd-auth]
# Same as above for Apache's mod_auth
# It catches wrong authentifications
port    = http,https
logpath = %(lighttpd_error_log)s


#
# Webmail and groupware servers
#

[roundcube-auth]

port     = http,https
logpath  = %(roundcube_errors_log)s
# Use following line in your jail.local if roundcube logs to journal.
#backend = %(syslog_backend)s


[openwebmail]

port     = http,https
logpath  = /var/log/openwebmail.log


[horde]

port     = http,https
logpath  = /var/log/horde/horde.log


[groupoffice]

port     = http,https
logpath  = /home/groupoffice/log/info.log


[sogo-auth]
# Monitor SOGo groupware server
# without proxy this would be:
# port    = 20000
port     = http,https
logpath  = /var/log/sogo/sogo.log


[tine20]

logpath  = /var/log/tine20/tine20.log
port     = http,https


#
# Web Applications
#
#

[drupal-auth]

port     = http,https
logpath  = %(syslog_daemon)s
backend  = %(syslog_backend)s

[guacamole]

port     = http,https
logpath  = /var/log/tomcat*/catalina.out

[monit]
#Ban clients brute-forcing the monit gui login
port = 2812
logpath  = /var/log/monit
           /var/log/monit.log


[webmin-auth]

port    = 10000
logpath = %(syslog_authpriv)s
backend = %(syslog_backend)s


[froxlor-auth]

port    = http,https
logpath  = %(syslog_authpriv)s
backend  = %(syslog_backend)s


#
# HTTP Proxy servers
#
#

[squid]

port     =  80,443,3128,8080
logpath = /var/log/squid/access.log


[3proxy]

port    = 3128
logpath = /var/log/3proxy.log


#
# FTP servers
#


[proftpd]

port     = ftp,ftp-data,ftps,ftps-data
logpath  = %(proftpd_log)s
backend  = %(proftpd_backend)s


[pure-ftpd]

port     = ftp,ftp-data,ftps,ftps-data
logpath  = %(pureftpd_log)s
backend  = %(pureftpd_backend)s


[gssftpd]

port     = ftp,ftp-data,ftps,ftps-data
logpath  = %(syslog_daemon)s
backend  = %(syslog_backend)s


[wuftpd]

port     = ftp,ftp-data,ftps,ftps-data
logpath  = %(wuftpd_log)s
backend  = %(wuftpd_backend)s


[vsftpd]
# or overwrite it in jails.local to be
# logpath = %(syslog_authpriv)s
# if you want to rely on PAM failed login attempts
# vsftpd's failregex should match both of those formats
port     = ftp,ftp-data,ftps,ftps-data
logpath  = %(vsftpd_log)s


#
# Mail servers
#

# ASSP SMTP Proxy Jail
[assp]

port     = smtp,465,submission
logpath  = /root/path/to/assp/logs/maillog.txt


[courier-smtp]

port     = smtp,465,submission
logpath  = %(syslog_mail)s
backend  = %(syslog_backend)s


[postfix]
# To use another modes set filter parameter "mode" in jail.local:
mode    = more
port    = smtp,465,submission
logpath = %(postfix_log)s
backend = %(postfix_backend)s


[postfix-rbl]

filter   = postfix[mode=rbl]
port     = smtp,465,submission
logpath  = %(postfix_log)s
backend  = %(postfix_backend)s
maxretry = 1


[sendmail-auth]

port    = submission,465,smtp
logpath = %(syslog_mail)s
backend = %(syslog_backend)s


[sendmail-reject]
# To use more aggressive modes set filter parameter "mode" in jail.local:
# normal (default), extra or aggressive
# See "tests/files/logs/sendmail-reject" or "filter.d/sendmail-reject.conf" for usage example and details.
#mode    = normal
port     = smtp,465,submission
logpath  = %(syslog_mail)s
backend  = %(syslog_backend)s


[qmail-rbl]

filter  = qmail
port    = smtp,465,submission
logpath = /service/qmail/log/main/current


# dovecot defaults to logging to the mail syslog facility
# but can be set by syslog_facility in the dovecot configuration.
[dovecot]

port    = pop3,pop3s,imap,imaps,submission,465,sieve
logpath = %(dovecot_log)s
backend = %(dovecot_backend)s


[sieve]

port   = smtp,465,submission
logpath = %(dovecot_log)s
backend = %(dovecot_backend)s


[solid-pop3d]

port    = pop3,pop3s
logpath = %(solidpop3d_log)s


[exim]
# see filter.d/exim.conf for further modes supported from filter:
#mode = normal
port   = smtp,465,submission
logpath = %(exim_main_log)s


[exim-spam]

port   = smtp,465,submission
logpath = %(exim_main_log)s


[kerio]

port    = imap,smtp,imaps,465
logpath = /opt/kerio/mailserver/store/logs/security.log


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

[courier-auth]

port     = smtp,465,submission,imap,imaps,pop3,pop3s
logpath  = %(syslog_mail)s
backend  = %(syslog_backend)s


[postfix-sasl]

filter   = postfix[mode=auth]
port     = smtp,465,submission,imap,imaps,pop3,pop3s
# 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  = %(postfix_log)s
backend  = %(postfix_backend)s


[perdition]

port   = imap,imaps,pop3,pop3s
logpath = %(syslog_mail)s
backend = %(syslog_backend)s


[squirrelmail]

port = smtp,465,submission,imap,imap2,imaps,pop3,pop3s,http,https,socks
logpath = /var/lib/squirrelmail/prefs/squirrelmail_access_log


[cyrus-imap]

port   = imap,imaps
logpath = %(syslog_mail)s
backend = %(syslog_backend)s


[uwimap-auth]

port   = imap,imaps
logpath = %(syslog_mail)s
backend = %(syslog_backend)s


#
#
# DNS servers
#


# !!! 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.
#
# IMPORTANT: see filter.d/named-refused for instructions to enable logging
# This jail blocks UDP traffic for DNS requests.
# [named-refused-udp]
#
# filter   = named-refused
# port     = domain,953
# protocol = udp
# logpath  = /var/log/named/security.log

# IMPORTANT: see filter.d/named-refused for instructions to enable logging
# This jail blocks TCP traffic for DNS requests.

[named-refused]

port     = domain,953
logpath  = /var/log/named/security.log


[nsd]

port     = 53
action   = %(banaction)s[name=%(__name__)s-tcp, port="%(port)s", protocol="tcp", chain="%(chain)s", actname=%(banaction)s-tcp]
           %(banaction)s[name=%(__name__)s-udp, port="%(port)s", protocol="udp", chain="%(chain)s", actname=%(banaction)s-udp]
logpath = /var/log/nsd.log


#
# Miscellaneous
#

[asterisk]

port     = 5060,5061
action   = %(banaction)s[name=%(__name__)s-tcp, port="%(port)s", protocol="tcp", chain="%(chain)s", actname=%(banaction)s-tcp]
           %(banaction)s[name=%(__name__)s-udp, port="%(port)s", protocol="udp", chain="%(chain)s", actname=%(banaction)s-udp]
           %(mta)s-whois[name=%(__name__)s, dest="%(destemail)s"]
logpath  = /var/log/asterisk/messages
maxretry = 10


[freeswitch]

port     = 5060,5061
action   = %(banaction)s[name=%(__name__)s-tcp, port="%(port)s", protocol="tcp", chain="%(chain)s", actname=%(banaction)s-tcp]
           %(banaction)s[name=%(__name__)s-udp, port="%(port)s", protocol="udp", chain="%(chain)s", actname=%(banaction)s-udp]
           %(mta)s-whois[name=%(__name__)s, dest="%(destemail)s"]
logpath  = /var/log/freeswitch.log
maxretry = 10


# enable adminlog; it will log to a file inside znc's directory by default.
[znc-adminlog]

port     = 6667
logpath  = /var/lib/znc/moddata/adminlog/znc.log


# To log wrong MySQL access attempts add to /etc/my.cnf in [mysqld] or
# equivalent section:
# log-warnings = 2
#
# for syslog (daemon facility)
# [mysqld_safe]
# syslog
#
# for own logfile
# [mysqld]
# log-error=/var/log/mysqld.log
[mysqld-auth]

port     = 3306
logpath  = %(mysql_log)s
backend  = %(mysql_backend)s


# Log wrong MongoDB auth (for details see filter 'filter.d/mongodb-auth.conf')
[mongodb-auth]
# change port when running with "--shardsvr" or "--configsvr" runtime operation
port     = 27017
logpath  = /var/log/mongodb/mongodb.log


# Jail for more extended banning of persistent abusers
# !!! WARNINGS !!!
# 1. 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
# 2. Increase dbpurgeage defined in fail2ban.conf to e.g. 648000 (7.5 days)
#    to maintain entries for failed logins for sufficient amount of time
[recidive]

logpath  = /var/log/fail2ban.log
banaction = %(banaction_allports)s
bantime  = 1w
findtime = 1d


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

[pam-generic]
# pam-generic filter can be customized to monitor specific subset of 'tty's
banaction = %(banaction_allports)s
logpath  = %(syslog_authpriv)s
backend  = %(syslog_backend)s


[xinetd-fail]

banaction = iptables-multiport-log
logpath   = %(syslog_daemon)s
backend   = %(syslog_backend)s
maxretry  = 2


# stunnel - need to set port for this
[stunnel]

logpath = /var/log/stunnel4/stunnel.log


[ejabberd-auth]

port    = 5222
logpath = /var/log/ejabberd/ejabberd.log


[counter-strike]

logpath = /opt/cstrike/logs/L[0-9]*.log
# Firewall: http://www.cstrike-planet.com/faq/6
tcpport = 27030,27031,27032,27033,27034,27035,27036,27037,27038,27039
udpport = 1200,27000,27001,27002,27003,27004,27005,27006,27007,27008,27009,27010,27011,27012,27013,27014,27015
action  = %(banaction)s[name=%(__name__)s-tcp, port="%(tcpport)s", protocol="tcp", chain="%(chain)s", actname=%(banaction)s-tcp]
           %(banaction)s[name=%(__name__)s-udp, port="%(udpport)s", protocol="udp", chain="%(chain)s", actname=%(banaction)s-udp]

[bitwarden]
port    = http,https
logpath = /home/*/bwdata/logs/identity/Identity/log.txt

[centreon]
port    = http,https
logpath = /var/log/centreon/login.log

# consider low maxretry and a long bantime
# nobody except your own Nagios server should ever probe nrpe
[nagios]

logpath  = %(syslog_daemon)s     ; nrpe.cfg may define a different log_facility
backend  = %(syslog_backend)s
maxretry = 1


[oracleims]
# see "oracleims" filter file for configuration requirement for Oracle IMS v6 and above
logpath = /opt/sun/comms/messaging64/log/mail.log_current
banaction = %(banaction_allports)s

[directadmin]
logpath = /var/log/directadmin/login.log
port = 2222

[portsentry]
logpath  = /var/lib/portsentry/portsentry.history
maxretry = 1

[pass2allow-ftp]
# this pass2allow example allows FTP traffic after successful HTTP authentication
port         = ftp,ftp-data,ftps,ftps-data
# knocking_url variable must be overridden to some secret value in jail.local
knocking_url = /knocking/
filter       = apache-pass[knocking_url="%(knocking_url)s"]
# access log of the website with HTTP auth
logpath      = %(apache_access_log)s
blocktype    = RETURN
returntype   = DROP
action       = %(action_)s[blocktype=%(blocktype)s, returntype=%(returntype)s,
                        actionstart_on_demand=false, actionrepair_on_unban=true]
bantime      = 1h
maxretry     = 1
findtime     = 1


[murmur]
# AKA mumble-server
port     = 64738
action   = %(banaction)s[name=%(__name__)s-tcp, port="%(port)s", protocol=tcp, chain="%(chain)s", actname=%(banaction)s-tcp]
           %(banaction)s[name=%(__name__)s-udp, port="%(port)s", protocol=udp, chain="%(chain)s", actname=%(banaction)s-udp]
logpath  = /var/log/mumble-server/mumble-server.log


[screensharingd]
# For Mac OS Screen Sharing Service (VNC)
logpath  = /var/log/system.log
logencoding = utf-8

[haproxy-http-auth]
# HAProxy by default doesn't log to file you'll need to set it up to forward
# logs to a syslog server which would then write them to disk.
# See "haproxy-http-auth" filter for a brief cautionary note when setting
# maxretry and findtime.
logpath  = /var/log/haproxy.log

[slapd]
port    = ldap,ldaps
logpath = /var/log/slapd.log

[domino-smtp]
port    = smtp,ssmtp
logpath = /home/domino01/data/IBM_TECHNICAL_SUPPORT/console.log

[phpmyadmin-syslog]
port    = http,https
logpath = %(syslog_authpriv)s
backend = %(syslog_backend)s


[zoneminder]
# Zoneminder HTTP/HTTPS web interface auth
# Logs auth failures to apache2 error log
port    = http,https
logpath = %(apache_error_log)s

[traefik-auth]
# to use 'traefik-auth' filter you have to configure your Traefik instance,
# see `filter.d/traefik-auth.conf` for details and service example.
port    = http,https
logpath = /var/log/traefik/access.log

Most common parameters

Most common jail.conf parameters are listed below:

[DEFAULT]

ignoreip = 127.0.0.1/8
bantime = 600
findtime = 600
maxretry = 3
usedns = warn
destemail = root@localhost
sendername = Fail2Ban
banaction = iptables-multiport
mta = sendmail
protocol = tcp
chain = INPUT
action = $(banaction_)s

# To use more aggressive sshd modes set filter parameter "mode" in jail.local:
# normal (default), ddos, extra or aggressive (combines all).
# See "tests/files/logs/sshd" or "filter.d/sshd.conf" for usage example and details.
#mode   = normal

port    = ssh
logpath = %(sshd_log)s
backend = %(sshd_backend)s

Number of retries

• maxretry: Max number of retries. It’s reasonable to set it to the same value as MaxAuthTries in the sshd_config.
  It can be done directly through command-line with:

  fail2ban-client set JAIL maxretry 5
  

• findtime: Max time for all of the retries. If they occur in that period, that host gets banned.
  i.E.: Let’s say we have 3 retries at max, and 600 seconds (10 minutes) for the findtime; if the user tries unsuccessfully to login after 3 tries within 10 minutes, that host is banned.
  It can be done directly through command-line with:

  fail2ban-client set JAIL findtime 600
  

Ban time

• bantime: The number of seconds that host is banned.
  It can be done directly through command-line with:

  fail2ban-client set JAIL bantime 600
  

• bantime.increment: If the ban time increases (true) or not (false) by a multiplier or a formula with a factor.

• bantime.rndtime: Max time in seconds that will be used for random ban time.

• bantime.maxtime: Max time in seconds that the ban can reach, that is, the limit.

• bantime.multipliers: Multipliers for the ban time considering the original ban time. Supossing 10 minutes of ban time (600 seconds), second ban will be 20 minutes, third 40 minutes, fourth 1h 20 minutes and so on. Example: bantime.multipliers = 1 2 4 8 16 32 64.

Ignore/Ban IP

• ignoreip: IPs or ranges of IPs that won’t get banned.
  It can be done directly through command-line with:

  fail2ban-client set JAIL addignoreip 192.168.1.0/24
  

• An IP can directly be banned through command line with: fail2ban-client set JAIL banip 254.3.6.18.

• It can also be unbanned with: fail2ban-client set JAIL unbanip 254.3.6.18.

Ban actions

The action parameter in jail.conf rules the action done when an IP gets banned. Default value is: action = %(action_)s.

Below there’s a list with more actions (only one can be used):

• Ban only: action = %(action_)s
• Ban and send email with whois report: action = %(action_mw)s
• Ban and send email with whois report and relevant log lines: action = %(action_mwl)s
• Ban and send a xarf e-mail to abuse contact of IP address and include relevant log lines: action = %(action_xarf)s
• Ban IP on Cloudfare and send email with whois report and relevant log lines: action = %(action_cf_mwl)s
• Report block via blocklist.de fail2ban reporting service API: action = %(action_blocklist_de)s
• Report ban via badips.com, and use as blacklist: action = %(action_badips)s
• Report ban via badips.com: action = %(action_badips_report)s
• Report ban via abuseipdb.com: action = %(action_abuseipdb)s