Are players glitching black ops?

[m9g]

I have been noticing more on black ops how hard it is to kill some players even to the point of shooting them point blank range for a couple of seconds and they then turn around and shoot me. Quite often aswell the will back out of the game right at the end.

Are they somehow glitching it? or am i being paranoid?

If there are glitches then what are they doing and how are they doing it?

Regards