fail2ban.conf fail2ban.d/*.conf fail2ban.local fail2ban.d/*.local
jail.conf jail.d/*.conf jail.local jail.d/*.local
DESCRIPTIONFail2ban has four configuration file types:
- Fail2Ban global configuration (such as logging)
- Filters specifying how to detect authentication failures
- Actions defining the commands for banning and unbanning of IP address
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
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.d/*.conf (in alphabetical order)
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]:
- indicates that the specified file is to be parsed before the current file.
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:
- verbosity level of log output: 1 = ERROR, 2 = WARN, 3 = INFO, 4 = DEBUG. Default: 1
- 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 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.
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.
- name of the filter -- filename of the filter in /etc/fail2ban/filter.d/ without the .conf/.local extension. Only one filter can be specified.
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(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:
- list of IPs not to ban. They can include a CIDR mask too.
- 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.
- effective ban duration (in seconds).
- time interval (in seconds) before the current time where failures will count towards a ban.
- number of failures that have to occur in the last findtime seconds to ban then IP.
- 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.
- 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)..
- 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).
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.
- command(s) executed when the jail starts.
- command(s) executed when the jail stops.
- command(s) ran before any other action. It aims to verify if the environment is still ok.
- command(s) that bans the IP address after maxretry log lines matches within last findtime seconds.
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 TagsThe following tags are substituted in the actionban, actionunban and actioncheck (when called before actionban/actionunban) commands.
- IPv4 IP address to be banned. e.g. 192.168.0.2
- number of times the failure occurred in the log file. e.g. 3
- UNIX (epoch) time of the ban. e.g. 1357508484
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:
- 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.
regex to identify log entries that should be ignored by Fail2Ban, even if they match failregex.
AUTHORFail2ban 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 BUGSReport bugs to https://github.com/fail2ban/fail2ban/issues
COPYRIGHTCopyright © 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.