a few searches on cod2 cheats found that some cheats for the game come with this file. I dont know if you add this file to your game dir, or if it overwrites the existing file in system. I'm assuming this PB check detects a different file size for it if it overwrites it or something like that.
Ive seen a few people kicked for it and a few kicked for blocking PB from scanning for it. I'm reluctant to ban ppl for this violation until I'm certain of its function though.