On an August workday in 2011, a cherubic 18-year-old Icelandic man named Sigurdur “Siggi” Thordarson walked through the stately doors of the U.S. embassy in Reykjavík, his jacket pocket concealing his calling card: a crumpled photocopy of an Australian passport. The passport photo showed a man with a unruly shock of platinum blonde hair and the name Julian Paul Assange.

Thordarson was long time volunteer for WikiLeaks with direct access to Assange and a key position as an organizer in the group. With his cold war-style embassy walk-in, he became something else: the first known FBI informant inside WikiLeaks. For the next three months, Thordarson served two masters, working for the secret-spilling website and simultaneously spilling its secrets to the U.S. government in exchange, he says, for a total of about $5,000. The FBI flew him internationally four times for debriefings, including one trip to Washington D.C., and on the last meeting obtained from Thordarson eight hard drives packed with chat logs, video and other data from WikiLeaks.

The relationship provides a rare window into the U.S. law enforcement investigation into WikiLeaks, the transparency group newly thrust back into international prominence with its assistance to NSA whistleblower Edward Snowden. Thordarson's double-life illustrates the lengths to which the government was willing to go in its pursuit of Julian Assange, approaching WikiLeaks with the tactics honed during the FBI’s work against organized crime and computer hacking — or, more darkly, the bureau’s Hoover-era infiltration of civil rights groups.

"It’s a sign that the FBI views WikiLeaks as a suspected criminal organization rather than a news organization," says Stephen Aftergood of the Federation of American Scientists’ Project on Government Secrecy. “WikiLeaks was something new, so I think the FBI had to make a choice at some point as to how to evaluate it: Is this The New York Times, or is this something else? And they clearly decided it was something else.”

The FBI declined comment.

Thordarson was 17 years old and still in high school when he joined WikiLeaks in February 2010. He was one of a large contingent of Icelandic volunteers that flocked to Assange’s cause after WikiLeaks published internal bank documents pertaining to that country’s financial crisis.

When a staff revolt in September 2010 left the organization short-handed, Assange put Thordarson in charge of the WikiLeaks chat room, making Thordarson the first point of contact for new volunteers, journalists, potential sources, and outside groups clamoring to get in with WikiLeaks at the peak of its notoriety.

In that role, Thordarson was a middle man in the negotiations with the Bradley Manning Defense Fund that led to WikiLeaks donating $15,000 to the defense of its prime source. He greeted and handled a new volunteer who had begun downloading and organizing a vast trove of 1970s-era diplomatic cables from the National Archives and Record Administration, for what became WikiLeaks’ “Kissinger cables” collection last April. And he wrangled scores of volunteers and supporters who did everything from redesign WikiLeaks' websites to shooting video homages to Assange.

He accumulated thousands of pages of chat logs from his time in WikiLeaks, which, he says, are now in the hands of the FBI.

Thordarson’s betrayal of WikiLeaks also was a personal betrayal of its founder, Julian Assange, who, former colleagues say, took Thordarson under his wing, and kept him around in the face of criticism and legal controversy.

“When Julian met him for the first or second time, I was there,” says Birgitta Jonsdottir, a member of Icelandic Parliament who worked with WikiLeaks on Collateral Murder, the Wikileaks release of footage of a US helicopter attack in Iraq. “And I warned Julian from day one, there’s something not right about this guy… I asked not to have him as part of the Collateral Murder team.”

In January 2011, Thordarson was implicated in a bizarre political scandal in which a mysterious “spy computer” laptop was found running unattended in an empty office in the parliament building. “If you did [it], don't tell me,” Assange told Thordarson, according to unauthenticated chat logs provided by Thordarson.

“I will defend you against all accusations, ring [sic] and wrong, and stick by you, as I have done,” Assange told him in another chat the next month. “But I expect total loyalty in return.”

Instead, Thordarson used his proximity to Assange for his own purposes. The most consequential act came in June 2011, on his third visit to Ellingham Hall — the English mansion where Assange was then under house arrest while fighting extradition to Sweden.

For reasons that remain murky, Thordarson decided to approach members of the Lulzsec hacking gang and solicit them to hack Islandic government systems as a service to WikiLeaks. To establish his bona fides as a WikiLeaks representative, he shot and uploaded a 40-second cell phone video that opens on the IRC screen with the chat in progress, and then floats across the room to capture Asssange at work with an associate. (This exchange was first reported by Parmy Olson in her book on Anonymous).

Unfortunately for Thordarson, the FBI had busted Lulzsec’s leader, Hector Xavier Monsegur, AKA Sabu, a week earlier, and secured his cooperation as an informant. On June 20, the FBI warned the Icelandic government. “A huge team of FBI came to Iceland and asked the Icelandic authorities to help them,” says Jonsdottir. “They thought there was an imminent Lulzsec attack on Iceland.”

The FBI may not have known at this point who Thordarson was beyond his screen names. The bureau and law enforcement agencies in the UK and Australia went on to round up alleged Lulzsec members on unrelated charges.

Having dodged that bullet, it’s not clear what prompted Thordarson to approach the FBI two months later. When I asked him directly last week, he answered, “I guess I cooperated because I didn't want to participate in having Anonymous and Lulzsec hack for Wikileaks, since then you’re definitely breaking quite a lot of laws.”

That answer doesn’t make a lot of sense, since it was Thordarson, not Assange, who asked Lulzsec to hack Iceland. There’s no evidence of any other WikiLeaks staffer being involved. He offered a second reason that he admits is more truthful: “The second reason was the adventure.”

Thordarson’s equivocation highlights a hurdle in reporting on him: He is prone to lying. Jonsdottir calls him “pathological.” He admits he has lied to me in the past. For this story, Thordarson backed his account by providing emails that appear to be between him and his FBI handlers, flight records for some of his travels, and an FBI receipt indicating that he gave them eight hard drives. The Icelandic Ministry of the Interior has previously confirmed that the FBI flew to Iceland to interview Thordarson. Thordarson also testified to much of this account in a session of the Icelandic Parliament, with Jonsdottir in attendance.

Finally, he has given me a substantial subset of the chat logs he says he passed to the FBI, amounting to about 2,000 pages, which, at the very least, proves that he kept logs and is willing to turn them over to a reporter disliked by Julian Assange.

Thordarson’s “adventure” began on August 23, 2011, when he sent an email to the general delivery box for the U.S. embassy in Reykjavík “Regarding an Ongoing Criminal investigation in the United States.”

“The nature of the intel that can be brought to light in that investigation will not be spoken over email conversation,” he wrote cryptically.

An embassy security officer called him the same day. “He said, 'What investigation?' I said the Wikileaks,” says Thordarson. “He denied there was such an investigation, so I just said we both know there is.”

Thordarson was invited to the embassy, where he presented a copy of Assange’s passport, the passport for Assange’s number two, Kristinn Hrafnsson, and a snippet of a private chat between Thordarson and Assange. The embassy official was noncommittal. He told Thordarson they might be in touch, but it would take at least a week.

It happened much faster.

Photo: Courtesy Sigurdur Thordarson

FBI agents and two federal prosecutors landed in a private Gulfstream on the next day, on August 24, and Thordarson was summoned back to the embassy.

He was met by the same embassy official who took his keys and his cell phone, then walked with him on a circuitous route through the streets of downtown Reykjavík, ending up at the Hotel Reykjavik Centrum, Thordarson says. There, Thordarson spent two hours in a hotel conference room talking to two FBI agents. Then they accompanied back to the embassy so he could put money in his parking meter, and back to the hotel for more debriefing.

The agents asked him about his Lulzsec interactions, but were primarily interested in what he could give them on WikiLeaks. One of them asked him if he could wear a recording device on his next visit to London and get Assange to say something incriminating, or talk about Bradley Manning.

“They asked what I use daily, have always on,” he says. “I said, my watch. So they said they could change that out for some recording watch.”

Thordarson says he declined. “I like Assange, even considered him a friend,” he says. “I just didn't want to go that way.”

In all, Thordarson spent 20 hours with the agents over about five days. Then the Icelandic government ordered the FBI to pack up and go home.

It turns out the FBI had misled the local authorities about its purpose in the country. According to a timeline (.pdf) later released by the National Commissioner of the Icelandic Police, the FBI contacted Icelandic law enforcement to report Thordarson's embassy walk-in, and ask for permission to fly into the country to follow up. But the bureau had presented the request as an extension of its earlier investigation into Lulzsec, and failed to mention that its real target was WikiLeaks.

WikiLeaks is well regarded in Iceland, and the incident errupted into a hot political topic when it surfaced there this year, with conservatives arguing that Iceland should have cooperated with the FBI, and liberals complaining about the agents being allowed into the country to begin with. "It became a massive controversy," says Jonsdottir. “And then none of them knew what sort of person Siggi is.”

Politics aside, the FBI was not done with Thordarson.

The agents persuaded Thordarson to fly to Copenhagen with them, he says, for another day of interviews. In October, he made a second trip to Denmark for another debriefing. Between meetings, Thordarson kept in touch with his handlers through disposable email accounts.

In November 2011, Thordarson was fired from WikiLeaks. The organization had discovered he had set up an online WikiLeaks tee shirt store and arranged for the proceeds to go into his own bank account. WikiLeaks has said the embezzlement amounted to about $50,000.

Thordarson told the FBI about it in a terse email on November 8. “No longer with WikiLeaks — so not sure how I can help you more.”

“We'd still like to talk with you in person,” one of his handlers replied. “I can think of a couple of easy ways for you to help.”

“Can you guys help me with cash?” Thordarson shot back.

Image: Courtesy Sigurdur Thordarson

For the next few months, Thordarson begged the FBI for money, while the FBI alternately ignored him and courted him for more assistance. In the end, Thordarson says, the FBI agreed to compensate him for the work he missed while meeting with agents (he says he worked at a bodyguard-training school), totaling about $5,000.

With the money settled, the FBI began preparing him for a trip to the U.S. “I wanted to talk to you about future things we can do,” his handler wrote in February. The FBI wanted him to reestablish contact with some of his former WikiLeaks associates. “We'll talk about specific goals of the chats, but you can get a head start before our meet by just getting in touch and catching up with them. If you need to know who specifically, we can discuss on the phone.”

The three-day D.C. trip took place in February of last year. Thordarson says he flew on Iceland Air flight 631 to Logan International Airport on February 22, and transferred in Boston to JetBlue flight 686 to Dulles International Aiport, where he was greeted by a U.S. Customs official “and then escorted out the Dulles terminal into the arms of the FBI.”

He stayed at a hotel in Arlington, Virginia, where the Justice Department’s investigation into WikiLeaks is centered, and met there with his two usual FBI contacts, and three or four other men in suits who did not identify themselves.

“At the last day we went to a steak house and ate, all of us,” he says. “Where they served Coca Cola in glass bottles from Mexico.”

On March 18, 2012, he had one more meeting with the FBI in Denmark. On this trip, he brought along eight of his personal hard drives, containing the information he’d compiled while at WikiLeaks, including his chat logs, photos and videos he shot at Ellingham Hall. The FBI gave him a signed receipt for the hardware.

Then they cut him off.

Today, Thordarson, now 20, has new problems. He’s facing criminal charges in Iceland for unrelated financial and tax crimes. In addition, WikiLeaks filed a police report for the tee-shirt shop embezzlement.

The legacy of his cooperation with the FBI is unclear. A court filing revealed last week shows that in the months following Thordarson ’s last debriefing, Justice Department officials in Arlington, Virginia, began obtaining court orders targeting two of Thordarson ’s former WikiLeaks colleagues in Iceland: Smari McCarthy and Herbert Snorrason.

Snorrason, who ran the WikiLeaks chat room in 2010, before Thordarson took it over, had the entire contents of his Gmail account handed over to the government, under a secret search warrant issued in October 2011.

The evidence used to obtain the warrant remains under seal. “I do wonder,” says Thordarson, “whether I’m somewhere in there.”