Wallhacking allows a player to see through solid or opaque objects and/or manipulate or remove textures, to know in advance when an opponent is about to come into targeting range from an occluded area. This can be done by making wall textures transparent, or modifying the game maps to insert polygonal holes into otherwise solid walls.
As with the aimbot, wallhacking relies on the fact that an FPS server usually sends raw positional information for all players in the game, and leaves it up to the client's 3D renderer to hide opponents behind walls, in plant foliage, or in dark shadows. If the game map rendering could be turned off completely, all players could be seen moving around in what appears to be empty space. Complete map hiding offers no advantage to a cheater as they would be unable to navigate the invisible map pathways and obstacles. However if only certain surfaces are made transparent or removed, this leaves just enough of an outline of the world to allow the cheater still to navigate it easily.
When used in conjunction certain wallhacks allow the player to shoot through solid objects, which is known as "opk" (One Place Killing) in such games as Combat Arms, because the killer can generally stay in one spot. A subset known as WhiteWalls removes the color/texture from objects in the surrounding environment, providing distinct contrast to opposition character models, which remain colored/textured. (See ESP for an evolution of the WallHack.) A subset of wallhacking is also called "chamming".
