(CNN) -- Spies with surveillance agencies in the United States and United Kingdom may have spent time undercover as orcs and blood elves, infiltrating video games like "World of Warcraft" in a hunt for terrorists "hiding in plain sight" online.
That's the finding of the most recent round of documents released by National Security Agency leaker Edward Snowden to British newspaper The Guardian.
Agents from the CIA, FBI and Pentagon and England's Government Communications Headquarters infiltrated WoW and virtual world "Second Life," as well as collecting information on the Xbox Live gaming network, according to the documents.
A 2008 NSA memo called online gaming a "target-rich communications network" where terrorists could communicate "in plain sight."
But apparently so many agents were engaged in playing video games for national security that a "deconfliction" group was created to make sure government agents weren't accidentally spying on each other.
Unlike traditional console and desktop games in which players compete in a closed environment, massively multiplayer online games (MMOs) allow players from around the world to team up and play together, often in real time using in-game communication tools.
"World of Warcraft" is the most popular online role-playing game ever. It peaked at about 12 million subscribers in 2010 and still has more than 7 million, according to Blizzard.
It's unclear whether the agencies had surveillance capabilities within the massively multi-player games that normal players would not. A spokesman for Blizzard Entertainment, which owns "World of Warcraft," told The Guardian it is unaware of any surveillance having taken place.
"If it was, it would have been done without our knowledge or permission," the spokesman said.
On Friday, Microsoft announced it was strengthening encryption across many of its services in an effort to push back against "government snooping."
And Monday, the company joined Google, Facebook, Yahoo, Apple, Twitter and LinkedIn issuing a public statement asking the world's governments to rein in online surveillance.
While acknowledging the scope and popularity of online gaming, some security experts were questioning Monday whether spying on digital playgrounds is either wise or effective.
"I think I've heard it all now," wrote British security analyst Graham Cluely.
"Obviously online games which include chat or IM facilities do provide a method for people to communicate ... but how practical is it to have a team of spies sniffing around 'World of Warcraft' to see what they might find?" he wrote.
"Why aren't they also snooping -- maybe they are! -- on the chess app I have on my smartphone? Perhaps every time I mess up my Dutch Stonewall defence it's not really an indication that I'm a lousy chess student, but instead a coded message for my opponent to launch an attack on SCADA systems in the Netherlands?"
Snowden, 30, has admitted he was the source behind the leak of classified NSA documents, which revealed the existence of top-secret surveillance programs that collect records of domestic e-mails and telephone calls in the United States and monitor the cell phone and Internet activity of overseas residents.
A former contractor with the agency, he is wanted in the United States on espionage charges.