The hack gives people any of the following: autoregenerating ammo, enhanced aim assist, enhanced jump, increased bullet damage, a wallhack which places a green square on top of all enemies (its size being relative to how close they are), constant UAV, selective spawns.
Thats all I have gathered from the current hacked distopia that is CoD4.
In other news, I am good at this game. my K/D was a solid .5 because I sniped for my first 40 levels. I brought it up to a 1.0 starting at level 39 in 25 matches. I pulled massive K/Ds even in the games where my entire team went negative and the other team had spawn trapping hackers. I pulled a 7 feed on TDM at one point. They just kept spawning right in front of me. (That makes me moist)
I planned to start tryharding one day, and I did so with these classes.
MP5 @ Silencer / USP 45
Frag/Stun
-Bandolier
-Stopping power
-Steady Aim
The MP5 has the perfect amount of kick at all ranges for me. Up close, Steady Aim provides quick kills and the ability to handle multiple players at once, especially since I common play groundwar. Stopping Power ensures that I don't get frustrated with having to use 5 bullets to kill at long ranges. I burst fire and usually pull what seems to be 3-4.
AK74u @ Silencer / USP 45
Frag/Stun
-Bandolier
-UAV Jammer
-Extreme Conditioning
This is my rushing/close range/midgame class. I usually use it once the other team starts to catch on to my patterns and starts pulling UAVs off of my bad teammates.
The 74u is a great weapon for close to mid range encounters and kills in a satisfactory amount of bullets at desired ranges for me. UAV jammer is there because I want to be unexpected. They shouldn't know that I'm coming so they can't prepare for me. Extreme conditioning is so I can abuse that they can't see me. Running is a stupid idea in any cod game unless its at the beginning of the match or you have cold blooded/ghost/UAV jammer.
R700 @ N/A / USP 45 (Dat remington)
Frag/Stun
-Bandolier
-Stopping Power
-Deep Impact
Everyone is on M40's ****. I like this gun more. I feel like I get less hitmarkers. There isn't much more reason.
Quickscoping in this game is fun, though, and feels like it takes a lot more skill than in MW2.