This hacker is getting me mad!! HELP ME

So I use jagerbomb and other small hacks in COD4 and whenever this guy comes in the server he has some kind of hack where when you shot him he does not die. His name is on both teams and its amazing how he hacks it like really crazy and makes all your hacks nothing. Whats possible hack does he have? What is the best hack out there? He is playing right now in there same server all the time..

No one can help me on this?

It's an exploit.

I dont understand