You don't necessarily have to hack anything to cheat at Call of Duty.
A group of Call of Duty: Black Ops player earned themselves a temporary ban and a rank reset after Treyarch became aware of their efforts to cheat the system and rack up hundreds of kills through spawn camping.
The camping marathon took place during a Demolition game on the Havana map. Demolition features fixed spawns for both teams, making it a rather popular game mode with spawn campers.
As you can see in the video, the camper in question made a beeline for one of the spawn points and proceeded to knife people in the back as they appeared, and once he had amassed enough kills, he used the helicopter gunship to spray the spawn point with lead. By the end of the match, he had died eight times, but had killed 501 people. What's more his team mates had also been camping and had similarly high scores.
Unfortunately - for the campers at least - one of the players filmed the match and put it up on YouTube, where Treyarch's community manager Josh Olin saw it and gave everyone involved a temporary ban and reset their rank to zero. According to Olin's Twitter replies, the opposing team was in cahoots with the campers, which is why they didn't just disconnect, so they earned bans as well. Olin said that spawn camping was a form of boosting, and wouldn't be tolerated in Black Ops.
Source: Game Culture