"We are unaware of any surveillance taking place," said a spokesman for Blizzard Entertainment, based in Irvine, Calif., which makes World of Warcraft. "If it was, it would have been done without our knowledge or permission."
A spokeswoman for Microsoft declined to comment. Philip Rosedale, the founder of Second Life and a former chief executive officer of Linden Lab, the game's maker, declined to comment on the spying revelations. Current Linden executives did not respond to requests for comment.
A Government Communications Headquarters spokesman would neither confirm nor deny any involvement by that agency in gaming surveillance, but said that its work is conducted under "a strict legal and policy framework" with rigorous oversight. An NSA spokeswoman declined to comment.
Intelligence and law enforcement officials became interested in games after some became enormously popular, drawing tens of millions of people worldwide, from preteens to retirees. The games rely on lifelike graphics, virtual currencies and the ability to speak to other players in real time. Some gamers merge the virtual and real worlds by spending long hours playing and making close online friends.
In World of Warcraft, players share the same fantasy universe -- walking around and killing computer-controlled monsters or the avatars of other players, including elves, animals or creatures known as orcs. In Second Life, players create customized human avatars that can resemble themselves or take on other personas -- supermodels and bodybuilders are popular -- who can socialize, buy and sell virtual goods, and go places like beaches, cities, art galleries and strip clubs. In Microsoft's Xbox Live service, subscribers connect online in games that can involve activities like playing soccer or shooting at each other in space.
According to American officials and documents that Mr. Snowden provided to The Guardian, which shared them with The New York Times and ProPublica, spy agencies grew worried that terrorist groups might take to the virtual worlds to establish safe communications channels.
In 2007, as the NSA and other intelligence agencies were beginning to explore virtual games, NSA officials met with the chief technology officer for the manufacturer of Second Life, the San Francisco-based Linden Lab. The executive, Cory Ondrejka, was a former Navy officer who had worked at the NSA with a top-secret security clearance.
He visited the agency's headquarters at Fort Meade, Md., in May 2007 to speak to staff members over a brown bag lunch, according to an internal agency announcement. "Second Life has proven that virtual worlds of social networking are a reality: come hear Cory tell you why!" said the announcement. It added that virtual worlds gave the government the opportunity "to understand the motivation, context and consequent behaviors of non-Americans through observation, without leaving U.S. soil."
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