What hacks are being used against me in PS3 Black Ops?

I would like details and what to look for if people are using hacks. It seems as though a lot more people are killing me out of nowhere. I am not the best player and I am not the worst. I will admit when I suck and did something stupid to die. But we all know that some things are fishy. Its free points to whoever gives me the best most detailed answer.