Heres a tricky one.
once you have built your password controller with black and white lists, post some black ones on the internet on another site you control, not only do you automatically turn off machines with people who try to use them but you get the ip address of the fool whos trying to stuff you around and a mac address if you want from there as well.
Basically posting black numbers will get fed around most other sites until they realize it doesnt work.
The other aspect to your game is to not give the information straight away its a black number.
In about 15 minutes, (just enough to get into it) of playing have the whole game crumble to a heap or make every monster have unlimited hit points.
Not only do you frustrate the cheater / player who's trying to cheat, but you also control black numbers within your software package.
haha.