[NA_Harlequin]

Well the scanner actively scans the installation directory, including file names and file sizes. Anything that's out of the ordinary is picked up and the player is kicked. Not only does it scan the MoH:AA directory however, but it scans the entire system, so we can see any background applications that may be running. I'm not saying that this method is infallible, but it at least eliminates a good deal of the most common cheats.