WikiLeaks supporters struck back on Wednesday at perceived enemies of founder Julian Assange, attacking the websites of Swedish prosecutors, the Swedish lawyer whose clients have accused Assange of sexual crimes and the Swiss authority that froze Assange’s bank account.

MasterCard, which pulled the plug on its relationship with WikiLeaks on Tuesday, also seemed to be having severe technological problems.

The online vengeance campaign appeared to be taking the form of denial of service attacks in which computers across the Internet are harnessed, sometimes surreptitiously, to jam target sites with mountains of requests for data, knocking them out of commission.

The online attacks are part of a wave of online support for WikiLeaks that is sweeping the Internet. Twitter was choked with messages of solidarity on Wednesday, while the site’s Facebook page hit one million fans.

Offline, the organization is under pressure on many fronts. Assange, its founder, is in a U.K. prison fighting extradition to Sweden over the sex crimes case, while moves by Swiss Postfinance, MasterCard, PayPal Inc. and others have impaired the secret-spilling group’s ability to raise money. The U.S. government is also investigating whether Assange can be prosecuted for espionage or other offenses.

Per Hellqvist, a security specialist with the firm Symantec, said a loose network of web activists called “Anonymous” appeared to be behind the attacks. The group, which has previously focused on the Church of Scientology and the music industry, has promised to come to Assange’s aid by knocking offline websites seen as hostile to WikiLeaks.

“While we don’t have much of an affiliation with WikiLeaks, we fight for the same reasons,” the group said in a statement on its website. “We want transparency and we counter censorship. ... This is why we intend to utilize our resources to raise awareness, attack those against and support those who are helping lead our world to freedom and democracy.”

It was not immediately clear which attacks the group was responsible for, although activists on Twitter and other forums cheered the news of each one in turn.

The website for MasterCard, which has said it will no longer process donations to WikiLeaks, was either down or sluggish early Wednesday. The company said it was experiencing “heavy traffic” but did not elaborate.

The website for Swedish lawyer Claes Borgstrom, who represents the two women at the centre of Assange’s sex crimes case, was unreachable on Wednesday.

The Swiss postal system’s financial arm, Postfinance, which shut down Assange’s new bank account on Monday, was also having trouble. Spokesman Alex Josty said the website buckled under a barrage of traffic on Tuesday but the onslaught seems to have eased off.

“Yesterday it was very, very difficult, then things improved overnight,” he told The Associated Press. “But it’s still not entirely back to normal.”

While one Internet company after another has cut its ties to the websites amid intense U.S. government pressure, Amazon.com, PayPal, EveryDNS, the French government’s effort to stop a company there from hosting WikiLeaks has failed, at least for now.

The Web services company OVH, which is among those hosting the current site, wikileaks.ch, sought a ruling by two courts about the legality of hosting WikiLeaks in France. The judges said this week they couldn’t decide on the highly technical case right away.

WikiLeaks evoked the ire of the U.S. government last spring when it posted a gritty war video taken by Army helicopters showing troops gunning down two unarmed Reuters journalists. Since then, the organization has leaked some 400,000 classified U.S. war files from Iraq and 76,000 from Afghanistan that U.S. military officials say included names of U.S. informants and other information that could put people’s lives at risk.

The latest leaks have involved private U.S. diplomatic cables that included frank U.S. assessments of foreign nations and their leaders.

Those cables have had serious repercussions for the United States, embarrassing allies, angering rivals, and reopening old wounds across the world. Foreign powers have been pulling back from their dealings with the U.S. government since the documents hit the Internet, State and Defence department officials said on Tuesday, while the Israeli government complained that the crisis over the leaked files was distracting Washington from efforts to restart Mideast peace talks, something Washington has denied.

Although U.S. officials have directed their ire at Assange, Defense Secretary Robert Gates cheered the news of his arrest on Tuesday, even its allies have begun to question whether Washington is ultimately to blame.

“The core of all this lies with the failure of the government of the United States to properly protect its own diplomatic communications,” Australian Foreign Minister Kevin Rudd said on Wednesday, noting that the secret cables were widely available to hundreds of thousands of U.S. government employees.

“To have several million people on their distribution list for a quarter of a million cables, that’s where the problem lies,” Mr. Rudd added.

The latest U.S. cables released on Wednesday showed that the British government feared a furious Libyan reaction if the convicted Lockerbie bomber wasn’t set free and expressed relief when they learned that he would be released in 2009 on compassionate grounds.

Meanwhile, Assange faces a new extradition hearing in the U.K. next week, in which his lawyers say they will reapply for bail. The 39-year-old Australian denies two women’s allegations of rape, molestation and unlawful coercion. He has not been charged with any crime in Sweden and is fighting his extradition there.

In a Twitter message on Wednesday, WikiLeaks spokesman Kristinn Hrafnsson shrugged off all the challenges and noted that the site is mirrored in over 500 locations by supporters.

“The latest batch of cables were released (on Tuesday evening), and our media partners released their next batch of stories,” Mr. Hrafnsson said. “We will not be gagged, either by judicial action or corporate censorship ... WikiLeaks is still online.”

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