Federal agents have been asked to stay away from one of the world's biggest hacker gatherings. 
 
 Revelations about the scale of US government spying meant emotions in  the hacking world were "running high", said organisers of the Def Con  convention. 
  
 
 As a result, federal agents should take a "timeout" from Def Con this year. 
  
 
 The main Def Con event takes place in Las Vegas from 1 August and will  see 15,000 hackers debate security topics and demonstrate their coding  prowess. 
  
 
 Freely mix 
  
 
 The request was posted to the main Def Con webpage by Jeff Moss, the founder of the hacking conference. 
  
 
 In the past, he said, the convention had been an "open nexus" where  government security staffers and law enforcement agents could freely mix  and share ideas with the other hackers, researchers and security  professionals that attended. 
  
 
 "Our community operates in the spirit of openness, verified trust, and  mutual respect," he said, a state of affairs that had led to an exchange  of information that had seemed mutually beneficial. 
  
 
 However, wrote Mr Moss, many people now questioned that free exchange of  ideas in the wake of ongoing disclosures about the US National Security  Agency's Prism programme, which, since 2007, has been scooping up huge  amounts of data about people's online activity. 
  
 
 As a result, "it would be best for everyone involved if the feds call a 'timeout' and not attend Def Con this year," he wrote. 
  
 
 "A little bit of time and distance can be a healthy thing, especially when emotions are running high," Mr Moss told Reuters. 
  
 
 Despite the request, Def Con organisers were not going to be checking  the identities of everyone who attended to weed out federal agents and  send them packing, he added. 
  
 
 Paper plea 
  
 
 Def Con's request comes as Yahoo seeks permission to publish information  about a key legal case in 2008 that let the US government establish and  justify Prism. 
  
 
 Yahoo has filed legal papers asking for permission from the Foreign  Intelligence Surveillance Court (Fisc), which decides whether US  government departments such as the National Security Agency can carry  out surveillance programmes. 
  
 
 In 2008, Yahoo had "objected strenuously" to the Fisc over requests for  it to co-operate with the early Prism programme, it said. But its  objections had been over-ruled by the Fisc.