Full brightness cheat

Full brightness is a multiplayer cheat which causes the screen to always be rendered at full brightness. The effect is similar to the lite amp power up, but permanent. This is considered a cheat as it gives the cheating player an unfair advantage over other players: in dark areas, the player will be able to see opponents perfectly.

The cheat takes the form of a PWAD loaded at startup or a modified IWAD file, to change the COLORMAP lump. Each light level map in the colormap is changed to be equal to the full brightness colormap.

The only conclusive way to detect the use of this cheat is visual observation of the player's screen as the game is played. However, on maps with extremely dark areas, viewing deathmatch recordings in which the cheat was loaded by one of the players could reveal circumstantial evidence.

Source

 * This writeup includes text from Bright Doom2 cheat modification, used with permission.