Appelbaum filled in for Wikileaks founder Julian Assange at the Next HOPE hacker conference in New York in mid-July. Assange, the voice and face of Wikileaks, skipped the appearance, anticipating that Department of Homeland Security agents might be waiting for him.
Applebaum's appearance at Defcon was to discuss the Tor project. Tor anonymizes your browsing behavior by bouncing your TCP requests from intermediate site to intermediate site.
Applebaum is a Seattle-based programmer and U.S. citizen. When he arrived at the Newark, New Jersey, airport on a flight from Holland on Thursday morning, he was pulled aside by customs and border protection agents. They told him he was "randomly selected" for a security search, according to anonymous sources speaking to C|Net.
For a random search, however, they seemed to know quite a bit about Appelbaum. The agents asked him for the location of Julian Assange. They also asked him questions about Wikileaks in general, as well as for his opinions on the wars in Afghanistan and Iraq. He was also frisked and his luggage searched.
Although Appelbaum has admitted ties to Wikileaks, while at the Next HOPE conference, he emphasized the fact that he was not involved with any of the Afghanistan leaks. He added he had no access to any classified data, either.