How do i hack modern warfare 2?

ok so i saw this pretty sophisticated hack about a week ago, it was this guy playing s&d on modern warefare 2 for the ps3, when he played i saw he brought up a screen and liked turned himself invisible and invincible he had unlimited ammo,never had to reload, and he can call in any kill streak he wanted. he could manipulate the game any way he wanted too. how did he hack the game this way and how is he getting away with it, i added him as a friend and he is still playing it and hacking the same way. and more importantly how can i do it?