@RobMc
Go to spec, take a video of these people seeing through walls, one shot killing, having every perk etc and give it to an admin and they will be banned on the spot. If you feel something isn't right with a player then take matter into your own hands and video them playing.
Here's how:
1) activate the console in-game by pressing the console key, which is located just beneath ESC.
2) Enter "/record" into the console to start recording a demo. If you want your demo to have a specific name, for example in order to remember whom or what you recorded, use "/record DEMONAME" instead.
3) When done with the recording, either leave the server or enter "/stoprecord" into the console.
4) You can now retrieve the demo from your Call of Duty 4 directory, in the /main/demos folder.
If you recorded a demo on a modded server, then the directory is /mods/MODNAME/demos
Get the demo file send it to an admin and the player will be banned if they are hacking as you say. Or send it to me and I will ban them if they are hacking as you say they are.