This rule detects the potential execution of the `/etc/rc.local` script through the `already_running` event action created by the `rc-local.service` systemd service. The `/etc/rc.local` script is a legacy initialization script that is executed at the end of the boot process. The `/etc/rc.local` script is not enabled by default on most Linux distributions. The `/etc/rc.local` script can be used by attackers to persistently execute malicious commands or scripts on a compromised system at reboot. As the rc.local file is executed prior to the initialization of Elastic Defend, the execution event is not ingested, and therefore the `already_running` event is leveraged to provide insight into the potential execution of `rc.local`.