jail.conf - configuration for the fail2ban server
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 action.d/*.py
Fail2ban has four configuration file types:
- Fail2Ban global configuration (such as logging)
- Filters specifying how to detect authentication
- Actions defining the commands for banning and unbanning of
- Jails defining combinations of Filters with Actions.
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
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
- 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.
- to use a different log path
jail.d/01_enable.conf - to enable a
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
Using Python "string interpolation" mechanisms, other definitions are
allowed and can later be used within other definitions as %(name)s.
Additionally fail2ban has an extended interpolation feature named
(means last known option with name
). This interpolation makes possible to extend a stock filter
or jail regexp in .local file (opposite to simply set failregex/ignoreregex
that overwrites it), e.g.
baduseragents = IE|wget
failregex = %(known/failregex)s
Additionally to interpolation %(known/parameter)s
, that does not works
for filter/action init parameters, an interpolation tag
can be used (means last known init definition
of filters or actions with name parameter
). This interpolation makes
possible to extend a parameters of stock filter or action directly in jail
file without creating a separately
filter.d/*.local file, e.g.
test.method = GET
baduseragents = IE|wget
failregex = ^%(__prefix_line)\s+"<test.method>"\s+test\s+regexp\s+-\s+useragent=(?:<baduseragents>)
# use filter "test", overwrite method to "POST" and extend known bad agents with "badagent":
filter = test[test.method=POST, baduseragents="badagent|<known/baduseragents>"]
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.
These files have one section, [Definition].
The items that can be set are:
- verbosity level of log output: CRITICAL, ERROR, WARNING,
NOTICE, INFO, DEBUG. Default: ERROR
- log target: filename, SYSLOG, STDERR or STDOUT. Default:
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.
- Database filename. Default:
This defines where the persistent data for fail2ban is stored. This
persistent data allows bans to be reinstated and continue reading log
files from the last read position when fail2ban is restarted. A value of
None disables this feature.
- Database purge age in seconds. Default: 86400 (24hours)
This sets the age at which bans should be purged from the database.
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, separated by
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
Optional space separated option 'tail' can be added to the end of the path
to cause the log file to be read from the end, else default 'head' option
reads file from the beginning
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.
- encoding of log files used for decoding. Default value of
"auto" uses current system locale.
- banning action (default iptables-multiport) typically
specified in the [DEFAULT] section for all jails.
This parameter will be used by the standard substitution of action
and can be redefined central in the [DEFAULT] section inside
jail.local (to apply it to all jails at once) or separately in each
jail, where this substitution will be used.
- the same as banaction but for some
"allports" jails like "pam-generic" or
"recidive" (default iptables-allports).
- action(s) from /etc/fail2ban/action.d/ without the
Arguments can be passed to actions to override the default values from the
[Init] section in the action file. Arguments are specified by:
Values can also be quoted (required when value includes a ","). More
that one action can be specified (in separate lines).
- list of IPs not to ban. They can include a CIDR mask
- 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", "systemd" 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.
Available options are listed below.
- requires pyinotify (a file alteration monitor) to be
installed. If pyinotify is not installed, Fail2ban will use auto.
- requires Gamin (a file alteration monitor) to be installed.
If Gamin is not installed, Fail2ban will use auto.
- uses a polling algorithm which does not require external
- uses systemd python library to access the systemd journal.
Specifying logpath is not valid for this backend and instead
utilises journalmatch from the jails associated filter config.
Each jail can be configured with only a single filter, but may have multiple
actions. By default, the name of a action is the action filename, and in the
case of Python actions, the ".py" file extension is stripped. Where
multiple of the same action are to be used, the actname
option can be
assigned to the action to avoid duplication e.g.:
enabled = true
action = smtp.py[firstname.lastname@example.org, actname=smtp-chris]
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
file in the /etc/fail2ban/action.d
and override the required settings.
Action files have two sections, Definition
The [Init] section enables action-specific settings. In
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
The [Init] section allows for action-specific settings. In
these can be overwritten for a particular jail as
options to the jail. The following are special tags which can be set in the
- The maximum period of time in seconds that a command can
executed, before being killed.
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
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 "set
<JAIL> action <ACT>" 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> >>
The 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.
- As per failures, but total of all failures for that
ip address across all jails from the fail2ban persistent database.
Therefore the database must be set for this tag to function.
- As per ipfailures, but total based on the IPs
failures for the current jail.
- 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.
- As per matches, but includes all lines for the IP
which are contained with the fail2ban persistent database. Therefore the
database must be set for this tag to function.
- As per ipmatches, but matches are limited for the IP
and for the current jail.
Python based actions can also be used, where the file name must be
. The Python file must contain a variable Action
which points to Python class. This class must implement a minimum interface as
described by fail2ban.server.action.ActionBase
, which can be inherited
from to ease implementation.
Filter definitions are those in /etc/fail2ban/filter.d/*.conf
These are used to identify failed authentication attempts in log files and to
extract the host IP address (or hostname if usedns
Like action files, filter files are ini files. The main section is the
There are two filter definitions used in the [Definition] section:
- is the regex (regular expression) 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.
For multiline regexs the tag <SKIPLINES> should be used to
separate lines. This allows lines between the matched lines to continue to
be searched for other failures. The tag can be used multiple times.
- is the regex to identify log entries that should be ignored
by Fail2Ban, even if they match failregex.
Similar to actions, filters have an [Init] section which can be overridden in
. Besides the filter-specific settings, the filter
[Init] section can be used to set following standard options:
- specifies the maximum number of lines to buffer to match
multi-line regexs. For some log formats this will not required to be
changed. Other logs may require to increase this value if a particular log
file is frequently written to.
- specifies a custom date pattern/regex as an alternative to
the default date detectors e.g. %Y-%m-%d %H:%M(?::%S)?. For a list of
valid format directives, see Python library documentation for strptime
Also, special values of Epoch (UNIX Timestamp), TAI64N and
ISO8601 can be used.
NOTE: due to config file string substitution, that %'s must be
escaped by an % in config files.
- specifies the systemd journal match used to filter the
journal entries. See journalctl(1) and
systemd.journal-fields(7) for matches syntax and more details on
special journal fields. This option is only valid for the systemd
Similar to actions [Init] section enables filter-specific settings. All
parameters specified in [Init] section can be redefined or extended in
Filters can also have a section called [INCLUDES]. This is used to read other
- indicates that this file is read before the [Definition]
- indicates that this file is read after the [Definition]
Fail2ban was originally written by Cyril Jaquier
<email@example.com>. At the moment it is maintained and further
developed by Yaroslav O. Halchenko <firstname.lastname@example.org>, Daniel Black
<email@example.com> and Steven Hiscocks
<firstname.lastname@example.org> along with a number of contributors.
file shipped with Fail2Ban for a full list. Manual page
written by Daniel Black and Yaroslav Halchenko.
Report bugs to https://github.com/fail2ban/fail2ban/issues
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