first of all i did a bit of research and experimentation (please do not accuse me as being a hacker) into hacking/exploitation for Crysis 2. Its piss easy just using cheat engine and editing mem values in one method. Other methods rely on Crysis 2 being almost totally client sided with wep damage for MP being totally moddable with NOTEPAD. Also ranking can be done by editing the XP values for kills and achievements etc again all done with notepad. I am sorry to say this but countering the hackers requires an almost certain go back to drawing board start from scratch anti hack approach which has not been implemented in this case but should be in the near future.
Thanks
Spartan9567