The National Security Agency has been tracking users of online gaming since at least 2007.

A document released by NSA leaker Edward Snowden titled “Exploiting Terrorist Use of Games & Virtual Environments” says the NSA and their British counterpart would analyze in-game communications for the possibility they were being used by terrorist groups.

“[Certain] games offer realistic weapons training (what weapon to use against what target, what ranges can be achieved, even aiming and firing), military operations and tactics, photorealistic land navigation and terrain familiarization, and leadership skills,” the document reads. “Some of the 9-11 pilots had never flown a real plane, they had only trained using Microsoft’s Flight Simulator.”

The Guardian newspaper reports that agents even entered the virtual words as gamers in an attempt to extract information from members. The newspaper said so many agents in different groups were working on the program that they needed a ‘deconfliction’ group to make sure they weren’t spying on each other.

In addition to games like World of Warcraft and Second Life, the NSA reportedly also spied on the XBOX Live network hosted by Microsoft that has over 48 million users.