Microsoft have booted as many as 1 million players from its Xbox LIVE due to their belief that they modified their consoles to play illegally downloaded games.
"All consumers should know that piracy is illegal and that modifying their Xbox 360 console to play pirated discs violates the Xbox Live terms of use, will void their warranty, and result in a ban from Xbox Live," Microsoft said in a statement.
Copies of games reportedly show up on pirate sites prior to their release.
"The health of the video game business depends on customers paying for the genuine products and services they receive from manufacturers, retailers, and the third parties that support them," Microsoft said.
Xbox 360 consoles are equipped with Digital Rights Management technologies designed to detect pirated software, but some players have successfully "modded", or modified, their machines to circumvent DRM protections.
It was not immediately clear how Microsoft detected the mods.
Consoles banned from Xbox LIVE will still function if games are played offline, but players booted from the Xbox LIVE service will not be able to sign into their accounts or engage other players over the Internet.
One player, banned from Xbox LIVE, told the U.K.'s Radio 1 that he was "gutted" and "distraught" by the decision. The player admitted paying an electronics shop more than $100 to modify his Xbox so it could play pirated games.
The Xbox Live gaming service counts more than 20 million members, according to Microsoft.