This executable can run non-interactive system commands.
This function is performed by the privileged user if executed via sudo because the acquired privileges are not dropped.
fail2ban-client add x
fail2ban-client set x addaction x
fail2ban-client set x action x actionban /path/to/command
fail2ban-client start x
fail2ban-client set x banip 999.999.999.999
fail2ban-client set x unbanip 999.999.999.999
fail2ban-client stop x