Well, I know a little bit of GLua and admins
CAN'T scan your entire computer, only what's in Garry's Mod folder or below. This can be used to detect hacks who write things in this folder, like Scripthook ( it's not a hack but still ), admins can WRITE infos in garrysmod/data (delete any suspicious files) and in cl.db ( use
http://sqlitebrowser.org/ to check if there's something suspicious ), everyone can easily see Family Sharing with the Steam Web API
You don't need to format your PC just to use a hack