Chams

Overview
Chams, short for Chameleon (the changing of colors), is a form of hack, or wallhack, in which you can see through the wall. Everyone is also brightly colored (some newer versions of chams show people as shadows) making them easier to see. A color which is a single unichrome means the opposing player are behind a structure, but once it's a mix of two colors means that target areas are exposed.

This also colors a bomb planted in Search and Destroy, Frag Grenades, and other forms of thrown items, mines, or moving map objects such as the train in Junk Flea or the boats in Waverider.

Chams is considered to be hard to report to Nexon, since chams is only visible to the player using it. Chams are quite common among the Combat Arms hacking community as it is rare to be banned or suspended while it is in use.

You can tell people that are chamming if they fire when they come out of a hole to kill somebody. For example "Player A" was hiding in a nook in Two Towers and a guy was about to pass him but the guy was waiting at the door because he was talking. The other guy would use chams to see the other guy and kill him. Another method would be if a teammate is accused of chamming, you could walk over to him, and look closely at his movements based on his position. This may work better for some than others, and is harder to tell on bigger maps, especially Snow Valley. Also, their KDR, depending on the type of cham, could be anywhere from 0.5 (If a noob could see through walls, essentially) to 12 (This almost always means shooting through walls).

Trivia

 * Most people refer to hacks as "chams", though chams are actually a specific type of hack itself. Those who often hack are called "chammers".
 * The Satellite Scanner is said to give "legit chams" as it lets the user and his/her teammates to get the same effect of chams except with a prechosen blue color, highlights of other people only restriction, and time limit.