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Fail2ban operates by monitoring log files (e.g. /var/log/pwdfail, /var/log/auth.log, etc.) for selected entries and running scripts based on them. Most commonly this is used to block selected IP addresses that may belong to hosts that are trying to breach the system's security. It can ban any host IP that makes too many login attempts or performs any other unwanted action within a time frame defined by the administrator.
Fail2ban operates by monitoring log files (e.g. /var/log/pwdfail, /var/log/auth.log, etc.) for selected entries and running scripts based on them. Most commonly this is used to block selected IP addresses that may belong to hosts that are trying to breach the system's security. It can ban any host IP that makes too many login attempts or performs any other unwanted action within a time frame defined by the administrator.
Fail2ban is typically set up to unban a blocked host within a certain period, so as to not "lock out" any genuine connections that may have been temporarily misconfigured. However, an unban time of several minutes is usually enough to stop a network connection being flooded by malicious connections, as well as reducing the likelihood of a successful dictionary attack.
Fail2ban is typically set up to unban a blocked host within a certain period, so as to not "lock out" any genuine connections that may have been temporarily misconfigured. However, an unban time of several minutes is usually enough to stop a network connection being flooded by malicious connections, as well as reducing the likelihood of a successful dictionary attack.
After installation the most important core services (and some additional ones) are monitored by default without the need for manual configuration (see: [[#Services|Services]]).
{{Tip box|fail2ban is not only a tool against brute force attack on ssh but it can be a tool useful against http protocol attacks or [http://forums.contribs.org/index.php/topic,50162.msg252195.html#msg252195 spam attacks] on your server. See the [[Fail2ban#Jail.conf |jail section]]}}
{{Tip box|fail2ban is not only a tool against brute force attack on ssh but it can be a tool useful against http protocol attacks or [http://forums.contribs.org/index.php/topic,50162.msg252195.html#msg252195 spam attacks] on your server. See the [[Fail2ban#Jail.conf |jail section]]}}
config setprop fail2ban IgnoreIP 12.15.22.4,17.20.0.0/16
config setprop fail2ban IgnoreIP 12.15.22.4,17.20.0.0/16
signal-event fail2ban-conf
signal-event fail2ban-conf
{{Note box|<code>signal-event fail2ban-conf</code> effectively restarts the service and clears existing bans, but a suitable 'findtime' results in a reban. Be aware that the restart delay can be unexpectedly lengthy due to the resource intensive process of scanning the logs to reban offending addresses.}}
===Services===
===Services===
The following services are monitored, and fail2ban will ban client IP for '''BanTime''' if more than '''MaxRetry''' authentication failure occure in less than '''FindTime'''
The following services are monitored out of the box, and fail2ban will ban client IP for '''BanTime''' if more than '''MaxRetry''' authentication failure occure in less than '''FindTime'''
*ssh
*ssh