July 31, 2010 4:16 PM PDT

LAS VEGAS — A security researcher involved with the Wikileaks Web site was detained by U.S. agents at the border for three hours and questioned about the controversial whistleblower project as he entered the country on Thursday to attend a hacker conference, sources said on Saturday.

Left to right: David Molnar, Alexander Sotirov, Marc Stevens, Arjen Lenstra, Jacob Appelbaum.
Left to right: David Molnar, Alexander Sotirov, Marc Stevens, Arjen Lenstra, Jacob Appelbaum.

He was also approached by two FBI agents at the Defcon conference after his presentation on Saturday afternoon about the Tor Project.

Jacob Appelbaum, a Seattle-based programmer for the online privacy protection project called Tor, arrived at the Newark, New Jersey, airport from Holland flight Thursday morning when he was pulled aside by customs and border protection agents who told him he was randomly selected for a security search, according to the sources familiar with the matter who asked to remain anonymous.

Appelbaum, a U.S. citizen, was taken into a room, frisked and his bag was searched. Receipts from his bag were photocopied and his laptop was inspected but it’s not clear in what manner, the sources said. Officials from the Immigration and Customs Enforcement and the U.S. Army then told him he was not under arrest but was being detained, the sources said. They asked questions about Wikileaks, asked for his opinions about the wars in Iraq and Afghanistan and asked where Wikileaks founder Julian Assange is, but he declined to comment without a lawyer present, according to the sources. He was not permitted to make a phone call, they said.

After about three hours, Appelbaum was given his laptop back but the agents kept his three mobile phones, sources said.

Asked for comment, Appelbaum declined to talk to CNET. However, he made reference to his phone getting seized to Defcon attendees. Following a question-and-answer session after his talk on the Tor Project Appelbaum was asked by an attendee for his phone number. He replied “that phone was seized.”

Shortly thereafter two casually dressed men identified themselves as FBI agents and asked to talk to him.

“We’d like to chat for a few minutes,” one of the men said, adding “we thought you might not want to.” Appelbaum asked them if they were aware of “what happened to me?” and one of them replied “Yes, that’s why we’re here.”

“I don’t have anything to say,” Appelbaum told them. One of the agents said they were interested in hearing if “human rights” being “trampled” and said “sometimes it’s nice to have a conversation to flesh things out.”

Marcia Hofmann, an attorney at the Electronic Frontier Foundation, was in the room and asked if the agents were at the event in an official capacity or for personal reasons. “A little of both,” one of the said.

Appelbaum asked when his equipment would be returned and one of them said “We aren’t involved in that; we have no idea,” and walked away when Appelbaum declined to talk further.

The agents declined to identify themselves to CNET. They said they were attending the conference and declined to talk further.

Appelbaum is a hacker and security researcher who co-founded the Noisebridge hacker space in San Francisco’s Mission district. He’s also worked to bypass the security of “smart” parking meters, unearth flaws in Web security certificates, and discover a novel way to bypass hard drive encryption.

At the Next HOPE hacker conference in New York in mid-July, Appelbaum filled in for Julian Assange, the controversial figure who’s become the public face of Wikileaks. Assange skipped his appearance at Next HOPE on the expectation that Homeland Security agents would be looking for him. After his own presentation, Appelbaum beat a hasty exit and hopped on a flight to Europe.

While he was on stage at Next HOPE, Appelbaum urged the largely sympathetic audience to support Wikileaks by volunteering or by donating money, to address recent criticisms of the document-publishing Web site, and to boast that Wikileaks remains uncensorable. “You can try to take us down… but you can’t stop us,” he said. He also challenged modern U.S. foreign policy and called for civil disobedience by way of exposing heavily guarded secrets.

Appelbaum told the Next HOPE audience that although he’s significantly involved in Wikileaks, he has no access to classified U.S. data that may have been sent to the site.

(CNET’s Declan McCullagh contributed to this report.)