Fail2Ban is a security tool designed to protect servers from malicious activity by monitoring system logs and automatically banning suspicious IP addresses. This cheat sheet provides essential Fail2Ban commands for configuration, monitoring, and management.

Introduction:

Fail2Ban is widely used to enhance server security by preventing brute-force attacks, unauthorized access, and other malicious activities. It works by monitoring system logs for specific patterns and taking action, such as blocking IP addresses, when suspicious activity is detected.

Basic Commands:

CommandDescription
fail2ban-client statusDisplay the overall status of Fail2Ban.
fail2ban-client reloadReload Fail2Ban configuration without restarting.
fail2ban-client stopStop Fail2Ban service.
fail2ban-client startStart Fail2Ban service.

Listing and Displaying Information:

CommandDescription
fail2ban-client status [jail]Display status information for a specific jail.
fail2ban-client status --verboseDisplay detailed status information.
fail2ban-client show [jail]Display configuration settings for a specific jail.

Manipulating Jails:

CommandDescription
fail2ban-client set [jail] addignoreip [IP]Add an IP address to the ignore list for a jail.
fail2ban-client set [jail] delignoreip [IP]Remove an IP address from the ignore list for a jail.
fail2ban-client set [jail] banip [IP]Manually ban an IP address in a specific jail.
fail2ban-client set [jail] unbanip [IP]Unban a manually banned IP address in a jail.

Configuring Fail2Ban:

CommandDescription
fail2ban-client set [jail] enabled true/falseEnable or disable a specific jail.
fail2ban-client set [jail] bantime [seconds]Set the ban time for a specific jail in seconds.
fail2ban-client set [jail] findtime [seconds]Set the find time for a specific jail in seconds.
fail2ban-client set [jail] maxretry [attempts]Set the maximum number of retry attempts for a jail.

Monitoring Logs:

CommandDescription
fail2ban-client set [jail] logpath [path]Set the log file path for a specific jail.
fail2ban-client set [jail] logfile [file]Set the log file name for a specific jail.
fail2ban-client set [jail] findtime [seconds]Set the find time for a specific jail in seconds.
fail2ban-client set [jail] maxretry [attempts]Set the maximum number of retry attempts for a jail.

Miscellaneous:

CommandDescription
fail2ban-client pingCheck if the Fail2Ban server is responsive.
fail2ban-client reload [jail]Reload configuration and restart a specific jail.
fail2ban-client unban --allUnban all IP addresses across all jails.

Conclusion

Fail2Ban is a powerful tool for enhancing server security, and this cheat sheet provides essential commands for configuration, monitoring, and management. Whether you need to check the status, manipulate jails, or configure settings, these commands will help you effectively use Fail2Ban to protect your system from malicious activities.