Today we released the first of a number of security updates, accounts that we have identified as exploiting an unfair advantage have been reset and if the activity persists they will be banned permanently. If you find yourself being kicked from every MP game it is because our systems have detected you cheating. We will continue to update anti-cheat software in Crysis 2 and strive for a cheat-free community.

We've already noticed some people pointing fingers and accusing others of cheating when this may not necessarily be the case. There may be some remaining issues that are unrelated to cheating (things like port/firewall settings, or other random connection issues).
Please don't take the opportunity to harass people who may be having technical issues and calling them cheaters. The cheat protection will deal with cheaters, but not everyone having connection issues are having them in relation to anti-cheat.

So folks, in a nutshell, don't cheat on Crysis 2 or else Crytek will find you and it won't be pretty :P