The nearly 500,000 U.S. Army documents published by WikiLeaks this year didn’t mark the first time founder Julian Assange thumbed his nose at the Pentagon. A new documentary about the secret-spilling site captures Assange in a rare moment of reminiscence as he reflects on his hacking of a Defense Department network in the 1990s, where he evidently kept a backdoor in place for some two years.

The documentary WikiRebels, produced by Sveriges Television in Sweden, was recently posted on the web in four parts. It provides an overview of Assange and WikiLeaks from the time the site published a classified Army video last April showing an Apache gunship attack in Iraq, to the latest release of U.S. State Department cables.

It also includes interviews with several current and former WikiLeaks activists, including former spokesman Daniel Domscheit-Berg and Icelandic volunteer Herbert Snorrason, who discuss the internal conflict at WikiLeaks that led them to resign.

It’s a compelling documentary, even if it provides little new information. In one segment (above, at 3:53), Assange reflects on his work as a black hat hacker in the early 1990s, recalling wistfully how he and others hacked into the Pentagon’s Security Coordination Center. The SCC was a Chantilly, Virginia, office that handled computer security issues for MilNet — later NIPRNet — the U.S. military’s portion of the public internet.

“We had a backdoor in the U.S. military Security Coordination Center –- this is the peak security for controlling the security of MilNet … U.S. military internet. We had total control over this for two years,” he tells the interviewer.

A backdoor refers to a malicious tool that hackers place on a network, once they’ve gained entry, to provide them with easy and continued surreptitious access to the network, allowing them to come and go at will.

The Defense Department did not immediately respond to an inquiry about the decades-old hack. The statute of limitations, it should be noted, has long since expired.

The intrusion was previously mentioned in an early version of Assange’s bio published by WikiLeaks when the site launched in 2006, which reads in part: “As a teenager he became Australia’s most famous ethical computer hacker. After referrals from the United States government his phone was tapped in 1991, and he spent six years in court. He hacked thousand of systems, including the Pentagon and the U.S. military Security Coordination Center.”

Assange, who used the handles “Proff” and “Mendax” during his black hat years, teamed up with two other hackers who called themselves the International Subversives. The group broke into networks in Europe and the U.S., including networks belonging to NASA, the Defense Department and the Los Alamos National Laboratory. Assange continued the activity until he was 21, when he was charged with 31 counts of hacking and other related activities and ultimately pleaded guilty to 25 charges.

Currently, U.S. authorities are reportedly trying to build a conspiracy case against Assange for his WikiLeaks work that would likely revolve around the Computer Fraud and Abuse Act (CFAA), the federal anti-hacking legislation.

Alleged WikiLeaks source Bradley Manning, who is suspected of leaking the Iraq video and war documents to Assange, has been charged under the CFAA and the Espionage Act. The CFAA makes it illegal to gain unauthorized access on a computer network or to exceed authorized access, as Manning is accused of doing.

If U.S. authorities can show that Assange encouraged or advised Manning on how to obtain the classified documents or how to cover his tracks after downloading them, they could charge Assange with conspiracy in Manning’s unauthorized computer activity.

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