SYNOPSIS

fail2ban.conf fail2ban.d/*.conf fail2ban.local fail2ban.d/*.local

jail.conf jail.d/*.conf jail.local jail.d/*.local

action.d/*.conf action.d/*.local

filter.d/*.conf filter.d/*.local

DESCRIPTION

Fail2ban has four configuration file types:

fail2ban.conf

Fail2Ban global configuration (such as logging)

filter.d/*.conf

Filters specifying how to detect authentication failures

action.d/*.conf

Actions defining the commands for banning and unbanning of IP address

jail.conf

Jails defining combinations of Filters with Actions.

CONFIGURATION FILES FORMAT

*.conf files are distributed by Fail2Ban. It is recommended that *.conf files should remain unchanged to ease upgrades. If needed, customizations should be provided in *.local files. For example, if you would like to enable the [ssh-iptables-ipset] jail specified in jail.conf, create jail.local containing

jail.local

[ssh-iptables-ipset]

enabled = true

In .local files specify only the settings you would like to change and the rest of the configuration will then come from the corresponding .conf file which is parsed first.

jail.d/ and fail2ban.d/

In addition to .local, for jail.conf or fail2ban.conf file there can be a corresponding .d/ directory containing additional .conf files. The order e.g. for jail configuration would be:

jail.conf

jail.d/*.conf (in alphabetical order)

jail.local

jail.d/*.local (in alphabetical order).

i.e. all .local files are parsed after .conf files in the original configuration file and files under .d directory. Settings in the file parsed later take precedence over identical entries in previously parsed files. Files are ordered alphabetically, e.g.

fail2ban.d/01_custom_log.conf - to use a different log path

jail.d/01_enable.conf - to enable a specific jail

jail.d/02_custom_port.conf - to change the port(s) of a jail.

Configuration files have sections, those specified with [section name], and name = value pairs. For those name items that can accept multiple values, specify the values separated by spaces, or in separate lines space indented at the beginning of the line before the second value.

Configuration files can include other (defining common variables) configuration files, which is often used in Filters and Actions. Such inclusions are defined in a section called [INCLUDES]:

before

indicates that the specified file is to be parsed before the current file.

after

indicates that the specified file is to be parsed after the current file.

Using Python "string interpolation" mechanisms, other definitions are allowed and can later be used within other definitions as %(name)s. For example.

baduseragents = IE|wget

failregex = useragent=%(baduseragents)s

Comments: use '#' for comment lines and '; ' (space is important) for inline comments. When using Python2.X '; ' can only be used on the first line due to an Python library bug.

FAIL2BAN CONFIGURATION FILE(S) (fail2ban.conf)

These files have one section, [Definition].

The items that can be set are:

loglevel

verbosity level of log output: 1 = ERROR, 2 = WARN, 3 = INFO, 4 = DEBUG. Default: 1

logtarget

log target: filename, SYSLOG, STDERR or STDOUT. Default: STDERR . Only a single 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).

socket

socket filename. Default: /var/run/fail2ban/fail2ban.sock . This is used for communication with the fail2ban server daemon. Do not remove this file when Fail2ban is running. It will not be possible to communicate with the server afterwards.

pidfile

PID filename. Default: /var/run/fail2ban/fail2ban.pid. This is used to store the process ID of the fail2ban server.

JAIL CONFIGURATION FILE(S) (jail.conf)

The following options are applicable to any jail. They appear in a section specifying the jail name or in the [DEFAULT] section which defines default values to be used if not specified in the individual section.

filter

name of the filter -- filename of the filter in /etc/fail2ban/filter.d/ without the .conf/.local extension. Only one filter can be specified.

logpath

filename(s) of the log files to be monitored. Globs -- paths containing * and ? or [0-9] -- can be used however only the files that exist at start up matching this glob pattern will be considered.

Ensure syslog or the program that generates the log file isn't configured to compress repeated log messages to "*last message repeated 5 time*s" otherwise it will fail to detect. This is called RepeatedMsgReduction in rsyslog and should be Off.

action

action(s) from /etc/fail2ban/action.d/ without the .conf/.local extension. Arguments can be passed to actions to override the default values from the [Init] section in the action file. Arguments are specified by:

[name=value,name2=value,name3="values,values"]

Values can also be quoted (required when value includes a ","). More that one action can be specified (in separate lines).

ignoreip

list of IPs not to ban. They can include a CIDR mask too.

ignorecommand

command that is executed to determine if the current candidate IP for banning should not be banned. IP will not be banned if command returns successfully (exit code 0). Like ACTION FILES, tags like <ip> are can be included in the ignorecommand value and will be substituted before execution. Currently only <ip> is supported however more will be added later.

bantime

effective ban duration (in seconds).

findtime

time interval (in seconds) before the current time where failures will count towards a ban.

maxretry

number of failures that have to occur in the last findtime seconds to ban then IP.

backend

backend to be used to detect changes in the logpath. It defaults to "auto" which will try "pyinotify", "gamin" before "polling". Any of these can be specified. "pyinotify" is only valid on Linux systems with the "pyinotify" Python libraries. "gamin" requires the "gamin" libraries.

usedns

use DNS to resolve HOST names that appear in the logs. By default it is "warn" which will resolve hostnames to IPs however it will also log a warning. If you are using DNS here you could be blocking the wrong IPs due to the asymmetric nature of reverse DNS (that the application used to write the domain name to log) compared to forward DNS that fail2ban uses to resolve this back to an IP (but not necessarily the same one). Ideally you should configure your applications to log a real IP. This can be set to "yes" to prevent warnings in the log or "no" to disable DNS resolution altogether (thus ignoring entries where hostname, not an IP is logged)..

failregex

regex (Python regular expression) to be added to the filter's failregexes. If this is useful for others using your application please share you regular expression with the fail2ban developers by reporting an issue (see REPORTING BUGS below).

ignoreregex

regex which, if the log line matches, would cause Fail2Ban not consider that line. This line will be ignored even if it matches a failregex of the jail or any of its filters.

ACTION CONFIGURATION FILES (action.d/*.conf)

Action files specify which commands are executed to ban and unban an IP address.

Like with jail.conf files, if you desire local changes create an [actionname].local file in the /etc/fail2ban/action.d directory and override the required settings.

Action files have two sections, Definition and Init .

The [Init] section enables action-specific settings. In jail.conf/jail.local these can be overridden for a particular jail as options of the action's specification in that jail.

The following commands can be present in the [Definition] section.

actionstart

command(s) executed when the jail starts.

actionstop

command(s) executed when the jail stops.

actioncheck

command(s) ran before any other action. It aims to verify if the environment is still ok.

actionban

command(s) that bans the IP address after maxretry log lines matches within last findtime seconds.

actionunban

command(s) that unbans the IP address after bantime.

Commands specified in the [Definition] section are executed through a system shell so shell redirection and process control is allowed. The commands should return 0, otherwise error would be logged. Moreover if actioncheck exits with non-0 status, it is taken as indication that firewall status has changed and fail2ban needs to reinitialize itself (i.e. issue actionstop and actionstart commands).

Tags are enclosed in <>. All the elements of [Init] are tags that are replaced in all action commands. Tags can be added by the fail2ban-client using the setctag command. <br> is a tag that is always a new line (\n).

More than a single command is allowed to be specified. Each command needs to be on a separate line and indented with whitespace(s) without blank lines. The following example defines two commands to be executed.

 actionban = iptables -I fail2ban-<name> --source <ip> -j DROP
             echo ip=<ip>, match=<match>, time=<time> >> /var/log/fail2ban.log

Action Tags

The following tags are substituted in the actionban, actionunban and actioncheck (when called before actionban/actionunban) commands.

ip

IPv4 IP address to be banned. e.g. 192.168.0.2

failures

number of times the failure occurred in the log file. e.g. 3

time

UNIX (epoch) time of the ban. e.g. 1357508484

matches

concatenated string of the log file lines of the matches that generated the ban. Many characters interpreted by shell get escaped to prevent injection, nevertheless use with caution.

FILTER FILES (filter.d/*.conf)

Filter definitions are those in /etc/fail2ban/filter.d/*.conf and filter.d/*.local.

These are used to identify failed authentication attempts in log files and to extract the host IP address (or hostname if usedns is true).

Like action files, filter files are ini files. The main section is the [Definition] section.

There are two filter definitions used in the [Definition] section:

failregex

regex that will match failed attempts. The tag <HOST> is used as part of the regex and is itself a regex for IPv4 addresses (and hostnames if usedns). Fail2Ban will work out which one of these it actually is.

ignoreregex

regex to identify log entries that should be ignored by Fail2Ban, even if they match failregex.

AUTHOR

Fail2ban was originally written by Cyril Jaquier <[email protected]>. At the moment it is maintained and further developed by Yaroslav O. Halchenko <[email protected]>, Daniel Black <[email protected]> and Steven Hiscocks <[email protected]> along with a number of contributors. See THANKS file shipped with Fail2Ban for a full list. Manual page written by Daniel Black and Yaroslav Halchenko.

REPORTING BUGS

Report bugs to https://github.com/fail2ban/fail2ban/issues

COPYRIGHT

Copyright © 2013 the Fail2Ban Team
Copyright of modifications held by their respective authors.
Licensed under the GNU General Public License v2 (GPL) or (at your option) any later version.