One of the oldest and largest hacker conventions in the world has asked U.S. government agents to stay away this year, following the leak of documents revealing that the National Security Agency has a program that spies on the internet activities of foreign nationals overseas when they use U.S. providers such as Microsoft and Apple.

Def Con takes place Aug. 1-4 at the Rio Hotel and Casino in Las Vegas. It has long welcomed academics and federal agents, including those from the NSA, to "meet, share ideas and party on neutral territory" with hackers of all stripes, wrote conference founder Jeff Moss, known online as "The Dark Tangent," in a blog post Wednesday.

"When it comes to sharing and socializing with feds, recent revelations have made many in the community uncomfortable about this relationship," he added. "Therefore, I think it would be best for everyone involved if the feds call a 'time-out' and not attend Def Con this year. This will give everybody time to think about how we got here and what comes next."

Moss , who is a member of the U.S. government's Homeland Security Advisory Council, told Reuters that the decision was a "tough call," but that "a little bit of time and distance can be a healthy thing, especially when emotions are running high."

15,000 each year

However, he added that the conference will not be "going on a witch hunt or checking IDs and kicking people out."

Def Con, which attracts about 15,000 participants each year, typically features talks and demonstrations by some of the foremost hackers and internet security specialists around the world, hacking contests and a variety of social events.

Details of the NSA internet surveillance program, which reportedly collected files such as audio and email, were described in leaked documents and described in the U.K. newspaper The Guardian in June, along with another NSA program that collected the phone records of Americans. The information had been leaked by Edward Snowden, the employee of government contractor Booz Allen Hamilton.

Snowden, 30, is wanted by U.S. authorities, who have charged him under the Espionage Act with unauthorized communication of national defence information and wilful communication of classified intelligence, along with theft of government property.

As of Wednesday, he was believed to be still in the Moscow airport transit zone. He has applied for asylum in a number of countries, and has been offered asylum by Venezuela, but may not be able to travel there.

Def Con originally started in 1993 as a party Moss was co-organizing for members of a Canadian-based hacker network called Platinum Net. Moss's Canadian co-organizer disappeared partway through the process, so he ended up inviting the members of several other networks.

With files from Reuters