Adversaries may use a Login Hook to establish persistence executed upon user logon. A login hook is a plist file that points to a specific script to execute with root privileges upon user logon. The plist file is located in the /Library/Preferences/com.apple.loginwindow.plist file and can be modified using the defaults command-line utility. This behavior is the same for logout hooks where a script can be executed upon user logout. All hooks require administrator permissions to modify or create hooks.

Adversaries can add or insert a path to a malicious script in the com.apple.loginwindow.plist file, using the LoginHook or LogoutHook key-value pair. The malicious script is executed upon the next user login. If a login hook already exists, adversaries can add additional commands to an existing login hook. There can be only one login and logout hook on a system at a time.

Note: Login hooks were deprecated in 10.11 version of macOS in favor of Launch Daemon and Launch Agent