Some game cheats are created by the developers, but not all of them are. There is a multi-million dollar industry of independent game cheat developers and subscription-based communities that provide cheaters with information, software and connections.
In the early days of video games, cheats were added by developers to popular games as a sort of reward program for dedicated gamers. As online player-versus-player gaming has become popular, the incentive for developers to provide some players with advantages that others might not have knowledge of has vanished, since the players who are unable to or refuse to cheat often lose interest in the games. This change has left a market niche for game cheat developers. Much of what they do is completely legal.
Game administrators are now faced with the task of identifying and banning cheaters, and there are software applications such as Valve Anti-Cheat that assist them with the task.