WONID

From HLSW Wiki

WONID is a term used in online games as a unique identifier of players that have a legal, working account for the game. WONID is used to track players (and multiple names they use) between server connections, for giving administrative rights, and to prevent software piracy.

It was created to allow only players with valid original games to play online.

Later, few months after showing up od Steam it was shut down by Valve, forcing players to play on illegal servers or switch to Counter-Strike 1.6. After shutdown SteamID is used to track players on Half-Life and Source based games.