Fail2Ban
Links & Installation
Fail2ban Documentation
Linode Fail2ban Guide
sudo yum install fail2ban
sudo apt install fail2ban
sudo pacman -Syu fail2ban
etc..
Configuration Files
/etc/fail2ban/
To modify configs, copy any fail2ban.conf to fail2ban.local and modify the copied fail2ban.local configuration file. Fail2ban will automatically override the settings in fail2ban.conf with those in fail2ban.local
sudo cp /etc/fail2ban/fail2ban.conf /etc/fail2ban/fail2ban.local
jail.conf
This file is not intended to be modified directly. Run the command below to create a local configuration to edit -
sudo cp /etc/fail2ban/fail2ban.conf /etc/fail2ban/fail2ban.local
jail.local
This file holds all of your local fail2ban settings for this host. Some of the important lines and settings to look at are seen below
- ignoreip
- An IP address for fail2ban to ignore
- maxrety
- Number of retries before being locked out
#... File Reduced ...
# Destination email address used solely for the interpolations in
# jail.{conf,local,d/*} configuration files.
destemail = user@gmail.com
# Sender email address used solely for some actions
sender = admin@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 = mail
# Default protocol
protocol = tcp
#... File Reduced ...
# 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_mwl)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
enabled = true
port = 22
logpath = %(sshd_log)s
backend = %(sshd_backend)s
#... File Reduced ...
[nginx-http-auth]
enabled = true
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]
enabled = true
port = http,https
logpath = %(nginx_error_log)s
maxretry = 2
#... File Reduced ...
its important to notice the line action = %(action_mwl)s - this line defines which default action we will take when a fail2ban is broken. These actions are defined within our jail.local, but Ill paste them here as well
# 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, bantime="%(bantime)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, bantime="%(bantime)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, bantime="%(bantime)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, bantime="%(bantime)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
You can use any action above that you'd like, and even create your own or modify them as you see fit.
Log Files
/var/log/messages
Shows all failed log attemps, config changes