Fail2Ban consists of a client, server and configuration files to limit
brute force authentication attempts.
The server program fail2ban-server is responsible for monitoring
log files and issuing ban/unban commands. It gets configured through
a simple protocol by fail2ban-client, which can also read
configuration files and issue corresponding configuration commands to
For details on the configuration of fail2ban see the jail.conf(5)
manual page. A jail (as specified in jail.conf) couples filters and
actions definitions for any given list of files to get monitored.
For details on the command-line options of fail2ban-server see the
fail2ban-server(1) manual page.
For details on the command-line options and commands for configuring
the server via fail2ban-client see the fail2ban-client(1) manual page.
For testing regular expressions specified in a filter using the
fail2ban-regex program may be of use and its manual page is
Fail2Ban is able to reduce the rate of incorrect authentications attempts
however it cannot eliminate the risk that weak authentication presents.
Configure services to use only two factor or public/private authentication
mechanisms if you really want to protect services.
A local user is able to inject messages into syslog and using a Fail2Ban
jail that reads from syslog, they can effectively trigger a DoS attack against
any IP. Know this risk and configure Fail2Ban/grant shell access accordingly.