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JAIL.CONF(5) Fail2Ban Configuration JAIL.CONF(5)
NAME
jail.conf - configuration for the fail2ban server
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 action.d/*.py
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 re-
main 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 corre-
sponding .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 prece-
dence over identical entries in previously parsed files. Files are ordered alpha-
betically, 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.
Fail2ban has more advanced syntax (similar python extended interpolation). This extended
interpolation is using %(section/parameter)s to denote a value from a foreign section.
Besides cross section interpolation the value of parameter in [DEFAULT] section can be re-
trieved with %(default/parameter)s.
Fail2ban supports also another feature named %(known/parameter)s (means last known option
with name parameter). 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|%(my-settings/baduseragents)s
failregex = %(known/failregex)s
useragent=%(baduseragents)s
Additionally to interpolation %(known/parameter)s, that does not works for filter/action
init parameters, an interpolation tag <known/parameter> 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 inside
jail.conf/jail.local file without creating a separately filter.d/*.local file, e.g.
# filter.d/test.conf:
[Init]
test.method = GET
baduseragents = IE|wget
[Definition]
failregex = ^%(__prefix_line)\s+"<test.method>"\s+test\s+regexp\s+-\s+useragent=(?:<baduseragents>)
# jail.local:
[test]
# 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.
FAIL2BAN CONFIGURATION FILE(S) (fail2ban.conf)
The items that can be set in section [Definition] are:
loglevel
verbosity level of log output: CRITICAL, ERROR, WARNING, NOTICE, INFO, DEBUG,
TRACEDEBUG, HEAVYDEBUG or corresponding numeric value (50-5). Default: INFO (equal
20)
logtarget
log target: filename, SYSLOG, STDERR or STDOUT. Default: STDOUT if not set in
fail2ban.conf/fail2ban.local
Note. If fail2ban running as systemd-service, for logging to the systemd-journal,
the logtarget could be set to STDOUT
Only a single log target can be specified. If you change logtarget from the de-
fault value and you are using logrotate -- also adjust or disable rotation in the
corresponding configuration file (e.g. /etc/logrotate.d/fail2ban on Debian sys-
tems).
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.
dbfile Database filename. Default: /var/lib/fail2ban/fail2ban.sqlite3
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 po-
sition when fail2ban is restarted. A value of None disables this feature.
dbmaxmatches
Max number of matches stored in database per ticket. Default: 10
This option sets the max number of matched log-lines could be stored per ticket in
the database. This also affects values resolvable via tags <ipmatches> and <ipjail-
matches> in actions.
dbpurgeage
Database purge age in seconds. Default: 86400 (24hours)
This sets the age at which bans should be purged from the database.
The config parameters of section [Thread] are:
stacksize
Stack size of each thread in fail2ban. Default: 0 (platform or configured default)
This 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.
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 spec-
ified 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, separated by new lines.
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.
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 com-
press 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.
logencoding
encoding of log files used for decoding. Default value of "auto" uses current sys-
tem locale.
logtimezone
Force the time zone for log lines that don't have one.
If this option is not specified, log lines from which no explicit time zone has
been found are interpreted by fail2ban in its own system time zone, and that may
turn to be inappropriate. While the best practice is to configure the monitored ap-
plications to include explicit offsets, this option is meant to handle cases where
that is not possible.
The supported time zones in this option are those with fixed offset: Z, UTC[+-]hhmm
(you can also use GMT as an alias to UTC).
This option has no effect on log lines on which an explicit time zone has been
found. Examples:
logtimezone = UTC
logtimezone = UTC+0200
logtimezone = GMT-0100
banaction
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 rede-
fined 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.
banaction_allports
the same as banaction but for some "allports" jails like "pam-generic" or "re-
cidive" (default iptables-allports).
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 ac-
tion can be specified (in separate lines).
ignoreself
boolean value (default true) indicates the banning of own IP addresses should be
prevented
ignoreip
list of IPs not to ban. They can include a DNS resp. CIDR mask too. The option af-
fects additionally to ignoreself (if true) and don't need to contain own DNS resp.
IPs of the running host.
ignorecommand
command that is executed to determine if the current candidate IP for banning (or
failure-ID for raw IDs) should not be banned. The option affects additionally to
ignoreself and ignoreip and will be first executed if both don't hit.
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.
ignorecache
provide cache parameters (default disabled) for ignore failure check (caching of
the result from `ignoreip`, `ignoreself` and `ignorecommand`), syntax:
ignorecache = key="<F-USER>@<ip-host>", max-count=100, max-time=5m
ignorecommand = if [ "<F-USER>" = "technical" ] && [ "<ip-host>" = "my-host.example.com" ]; then exit 0; fi;
exit 1
This will cache the result of ignorecommand (does not call it repeatedly) for 5
minutes (cache time) for maximal 100 entries (cache size), using values substituted
like "user@host" as cache-keys. Set option ignorecache to empty value disables the
cache.
bantime
effective ban duration (in seconds or time abbreviation format).
findtime
time interval (in seconds or time abbreviation format) 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", "systemd" before
"polling". Any of these can be specified. "pyinotify" is only valid on Linux sys-
tems 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 res-
olution altogether (thus ignoring entries where hostname, not an IP is logged)..
prefregex
regex (Python regular expression) to parse a common part containing in every mes-
sage (see prefregex in section FILTER FILES for details).
failregex
regex (Python regular expression) to be added to the filter's failregexes (see
failregex in section FILTER FILES for details). 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.
maxmatches
max number of matched log-lines the jail would hold in memory per ticket. By de-
fault it is the same value as maxretry of jail (or default). This option also af-
fects values resolvable via tag <matches> in actions.
Backends
Available options are listed below.
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 in-
stalled, 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 and instead utilises journalmatch from the jails associ-
ated filter config. Multiple systemd-specific flags can be passed to the backend,
including journalpath and journalfiles, to explicitly set the path to a directory
or set of files. journalflags, which by default is 4 and excludes user session
files, can be set to include them with journalflags=1, see the python-systemd docu-
mentation for other settings and further details. Examples:
backend = systemd[journalpath=/run/log/journal/machine-1]
backend = systemd[journalfiles="/path/to/system.journal, /path/to/user.journal"]
backend = systemd[journalflags=1]
Actions
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.:
[ssh-iptables-ipset]
enabled = true
action = smtp.py[dest=chris AT example.com, actname=smtp-chris]
smtp.py[dest=sally AT example.com, actname=smtp-sally]
TIME ABBREVIATION FORMAT
The time entries in fail2ban configuration (like findtime or bantime) can be provided as
integer in seconds or as string using special abbreviation format (e. g. 600 is the same
as 10m).
Abbreviation tokens:
years?, yea?, yy?
months?, mon?
weeks?, wee?, ww?
days?, da, dd?
hours?, hou?, hh?
minutes?, min?, mm?
seconds?, sec?, ss?
The question mark (?) means the optional character, so day as well as days can be used.
You can combine multiple tokens in format (separated with space resp. without separator),
e. g.: 1y 6mo or 1d12h30m.
Note that tokens m as well as mm means minutes, for month use abbreviation mo or mon.
The time format can be tested using fail2ban-client:
fail2ban-client --str2sec 1d12h
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.
The [Init] section allows for action-specific settings. In jail.conf/jail.local these can
be overwritten for a particular jail as options to the jail. The following are special
tags which can be set in the [Init] section:
timeout
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 actionstop and actionstart commands). Tags are enclosed in <>. All the ele-
ments 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 al-
ways a new line (\n).
More than a single command is allowed to be specified. Each command needs to be on a sepa-
rate line and indented with whitespace(s) without blank lines. The following example de-
fines 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
ipfailures
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.
ipjailfailures
As per ipfailures, but total based on the IPs failures for the current jail.
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.
ipmatches
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.
ipjailmatches
As per ipmatches, but matches are limited for the IP and for the current jail.
PYTHON ACTION FILES
Python based actions can also be used, where the file name must be [actionname].py. 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 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] sec-
tion.
There are several standard filter definitions used in the [Definition] section:
prefregex
is the regex (regular expression) to parse a common part containing in every mes-
sage, which is applied after datepattern found a match, before the search for any
failregex or ignoreregex would start.
If this regex doesn't match the process is starting immediately with next message
and search for any failregex does not occur.
If prefregex contains <F-CONTENT>...</F-CONTENT>, the part of message enclosed be-
tween this tags will be extracted and herafter used as whole message for search
with failregex or ignoreregex.
For example:
prefregex = ^%(__prefix_line)s (?:ERROR|FAILURE) <F-CONTENT>.+</F-CONTENT>$
failregex = ^user not found
^authentication failed
^unknown authentication method
You can use prefregex in order to:
- specify 1 common regex to match some common part present in every messages
(do avoid unneeded match in every failregex if you have more as one);
- to cut some interesting part of message only (to simplify failregex) en-
closed between tags <F-CONTENT> and </F-CONTENT>;
- to gather some failure identifier (e. g. some prefix matched by <F-ML-
FID>...<F-MLFID/> tag) to identify several messages belonging to same ses-
sion, where a connect message containing IP followed by failure message(s)
that are not contain IP; this provides a new multi-line parsing method as
replacement for old (slow an ugly) multi-line parsing using buffering window
(maxlines > 1 and <SKIPLINES>);
- to ignore some wrong, too long or even unneeded messages (a.k.a. parasite
log traffic) which can be also present in journal, before failregex search
would take place.
failregex
is the regex (regular expression) that will match failed attempts. The standard re-
placement tags can be used as part of the regex:
<HOST> - common regex for IP addresses and hostnames (if usedns is enabled).
Fail2Ban will work out which one of these it actually is.
<ADDR> - regex for IP addresses (both families).
<IP4> - regex for IPv4 addresses.
<IP6> - regex for IPv6 addresses (also IP enclosed in brackets).
<DNS> - regex to match hostnames.
<CIDR> - helper regex to match CIDR (simple integer form of net-mask).
<SUBNET> - regex to match sub-net adresses (in form of IP/CIDR, also single
IP is matched, so part /CIDR is optional).
NOTE: the failregex will be applied to the remaining part of message after pre-
fregex processing (if specified), which in turn takes place after datepattern pro-
cessing (whereby the string of timestamp matching the best pattern, cut out from
the message).
For multiline regexs (parsing with maxlines greater that 1) the tag <SKIPLINES> can
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.
This is an obsolete handling and if the lines contain some common identifier, bet-
ter would be to use new handling (with tags <F-MLFID>...<F-MLFID/>).
ignoreregex
is the regex to identify log entries that should be ignored by Fail2Ban, even if
they match failregex.
maxlines
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.
datepattern
specifies a custom date pattern/regex as an alternative to the default date detec-
tors e.g. %%Y-%%m-%%d %%H:%%M(?::%%S)?. For a list of valid format directives, see
Python library documentation for strptime behaviour.
NOTE: due to config file string substitution, that %'s must be escaped by an % in
config files.
Also, special values of Epoch (UNIX Timestamp), TAI64N and ISO8601 can be used as
datepattern.
Normally the regexp generated for datepattern additionally gets word-start and
word-end boundaries to avoid accidental match inside of some word in a message.
There are several prefixes and words with special meaning that could be specified
with custom datepattern to control resulting regex:
{DEFAULT} - can be used to add default date patterns of fail2ban.
{DATE} - can be used as part of regex that will be replaced with default
date patterns.
{^LN-BEG} - prefix (similar to ^) changing word-start boundary to line-start
boundary (ignoring up to 2 characters). If used as value (not as a prefix),
it will also set all default date patterns (similar to {DEFAULT}), but an-
chored at begin of message line.
{UNB} - prefix to disable automatic word boundaries in regex.
{NONE} - value would allow to find failures totally without date-time in log
message. Filter will use now as a timestamp (or last known timestamp from
previous line with timestamp).
journalmatch
specifies the systemd journal match used to filter the journal entries. See jour-
nalctl(1) and systemd.journal-fields(7) for matches syntax and more details on spe-
cial journal fields. This option is only valid for the systemd backend.
Similar to actions, filters may have an [Init] section also (optional since v.0.10). All
parameters of both sections [Definition] and [Init] can be overridden (redefined or ex-
tended) in jail.conf or jail.local (or in related filter.d/filter-name.local). Every op-
tion supplied in the jail to the filter overwrites the value specified in [Init] section,
which in turm would overwrite the value in [Definition] section. Besides the standard
settings of filter both sections can be used to initialize filter-specific options.
Filters can also have a section called [INCLUDES]. This is used to read other configura-
tion files.
before indicates that this file is read before the [Definition] section.
after indicates that this file is read after the [Definition] section.
AUTHOR
Fail2ban was originally written by Cyril Jaquier <cyril.jaquier AT fail2ban.org>. At the mo-
ment it is maintained and further developed by Yaroslav O. Halchenko <debian@onerus-
sian.com>, Daniel Black <daniel.subs AT internode.net> and Steven Hiscocks <steven-
fail2ban AT hiscocks.uk> 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 (C) 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 ver-
sion.
SEE ALSO
fail2ban-server(1)
Fail2Ban November 2015 JAIL.CONF(5)
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