Warden (also known as Warden Client) is an anti-cheating tool integrated in Blizzard Entertainment games such as Diablo II (since patch 1.11), StarCraft (patch 1.15), Warcraft III and most notably World of Warcraft. While the game is running, Warden uses API function calls to collect data on open programs on the user's computer and sends it back to Blizzard servers as hash values to be compared to those of known cheating programs. Privacy advocates consider the program to be spyware.