The newly disclosed classified data said the operatives, fearing terrorist or criminal networks could use the video gaming world as a communications cover, created online personae to spy and try to recruit informants, the New York Times reported Monday.
The documents were disclosed by the former National Security Agency contractor Edward J. Snowden, the Times said.
While seemingly innocent, a top-secret 2008 NSA document warned such virtual games could be a "target-rich communication network" allowing suspects "a way to hide in plain sight."
The documents reported on Monday do not cite any counter-terrorism successes from infiltration into the virtual gaming world, and former U.S. intelligence officials, current and former gaming company employees and experts told the Times they knew of little evidence terrorist groups considered the games a way to communicate and plot operations.
Games "are built and operated by companies looking to make money, so the players' identity and activity is tracked," Brookings Institution analyst Peter W. Singer said. "For terror groups looking to keep their communications secret, there are far more effective and easier ways to do so than putting on a troll avatar."
The surveillance could raise privacy concerns, observers said. The Times said it was unclear how the agencies gained access to gamers' data or communications, how many players may have been monitored or whether Americans' communications or activities were captured.