A computer hacker who calls himself “The Jester” claimed responsibility for the cyber attack which took down the WikiLeaks site Sunday, shortly before it started posting hundreds of thousands of classified U.S. diplomatic cables.

The Jester, who describes himself as a “hacktivist for good,” said he took the controversial site down “for attempting to endanger the lives of our troops, ‘other assets’ & foreign relations.”

He normally attacks Islamist websites, announcing “TANGO DOWN” on his Twitter account when claiming to have attacked a site. “Tango Down” is Special Forces jargon for having eliminated a terrorist.

Over the past few days, the Jester has targeted a handful of websites for reasons including “online incitement to cause young Muslims to carry out acts of violent jihad,” “distributing jihadist instructional materials,” and “for the online radicalization of young Muslims in US and Europe.”

The Jester describes himself as “an ex-soldier with a rather famous unit, country purposely not specified.”

“I was involved with supporting Special Forces, I have served in (and around) Afghanistan amongst other places,” he told the website threatchaos.com early this year.

WikiLeaks said in September that it had prepared an unspecified “insurance policy” against its site being taken down.

“This annoyed me… so I got busy,” the Jester wrote on his blog in September.

The calls for an all-out campaign against WikiLeaks are growing more shrill. Tony Shaffer of the Center for Advanced Defense Studies, a former Defense Intelligence Agency officer, told Fox News that he would like to see military action against Assange: “I would look at this very much as a military issue. With potentially military action against him and his organization.” (While the Obama administration no longer uses the term “enemy combatant,” it claims (PDF) the authority to “detain” someone who has provided “substantial support” to enemies of the United States.

White House press secretary Robert Gibbs today said: “WikiLeaks and people that disseminate information to people like this are criminals, first and foremost. And I think that needs to be clear.” That’s an indication the investigation has gone beyond WikiLeaks’ source to the group itself. He added, when asked against legal action against WikiLeaks and Assange: “We are looking at a whole host of things, and I wouldn’t rule anything out.” And syndicated columnist Charles Krauthammer reportedly said on Fox News (I haven’t seen this segment myself yet) that journalists should be investigated: “To say that if you are unlike CNN and Wall Street Journal, who apparently turned down collaboration with WikiLeaks, and you collaborate, we are going to look into possible prosecution.”

Monique Wadsted, an attorney representing American record companies, was pleased with the ruling.

“It’s a relief that the court of appeal finally affirmed that if you carry out this type of activity, you’ll go to prison,” she told TT.

“In two years, this type of piracy will be over. After a ruling like this and all the pioneers start to get older and have children and families, piracy won’t occur to this extent.”

While Christian Engström, a member of the European Parliament representing the Pirate Party, called the ruling “depressing,” he disputed whether the ruling would affect file sharing.

“The judgement has no meaning for file sharing. It has continued to increase from year to year and the technical capabilities continue to develop,” he told TT.

He currently travels internationally between one and three times a month in connection with his company, Whisper Systems, which recently released two free encryption applications for Android phones that protect SMS messages and voice calls.

“They’re beginning to destroy my ability to run a business with international customers, ” he says. “I can’t travel internationally without assurances that I’m not going to spend 5 hours in a detention room and am not going to lose whatever electronic devices I have with me at the time.”