Steam has introduced a new system allowing game developers to ban individual
users (thanks
VG247). Here's how this works:
Banned by Game Developer (Game Ban)
Because nobody likes playing with cheaters.
Playing games should be fun. In order to ensure the best possible online
multiplayer experience, Valve allows developers to implement their own systems
that detect and permanently ban any disruptive players, such as those using
cheats.
Game developers inform Valve when a disruptive player has been detected in their
game, and Valve applies the game ban to the account. The game developer is
solely responsible for the decision to apply a game ban. Valve only enforces the
game ban as instructed by the game developer.
For more information about a game ban in a specific game, please contact the
developer of that game.