Updated at 2:29 p.m. ET
Websites that likely expected to be on the sidelines of the battle between the document-dumping organization WikiLeaks and governments for the United States and European nations have found themselves square in the crosshairs of hackers.
Skirmishes raged across in cyberspace Thursday between WikiLeaks supporters and the companies they accuse of trying to stifle the group, with websites on both sides of the battle line choked off by attacks.
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MasterCard Inc., Visa Inc., Amazon.com, PayPal Inc. and EveryDNS have cut their ties to WikiLeaks after the Obama administration and members of Congress put intense pressure on U.S.-based Internet companies.
Those moves have hurt WikiLeaks' ability to accept donations and support publishing efforts - and raised concerns at the United Nations. Hackers have responded by attempting to disrupt MasterCard, PayPal and Visa's websites by flooding them with traffic. Some have even threatened to attack Amazon's online retail site.
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The attacks on WikiLeaks' perceived foes continued Thursday, rendering PayPal's blog unreachable and targeting the popular online payment service's infrastructure. The loose-knit online collective Anonymous - which has claimed responsibility for the cyber-assaults in defense of WikiLeaks - said it was fighting "against those who seek to misuse the Internet," according to an unsigned pamphlet that circulated Thursday on Twitter.
Anonymous has also suffered online setbacks. Its main website was unreachable Thursday, while a Twitter account held in Anonymous's name was also pulled. Neither development seemed to stop supporters from distributing software used to overwhelm target websites with requests for data.
Similarly, Facebook confirmed Thursday it had deleted the account of some cyber activists because they promoted the online attacks, the Reuters news agency reported. Twitter and Facebook seem to be immune to the attacks troubling MasterCard, PayPal and Visa possibly because they serve as a way for activists and WikiLeaks to communicate to a mass audience.
The attacks haven't gone unnoticed by the U.S. government. Attorney General Eric Holder said Thursday that the Justice Department was "looking into" them, Bloomberg News reported. Similarly, Homeland Security Secretary Janet Napolitano said the government was coordinating with the "private sector" on cyber issues, Bloomberg reported.
WikiLeaks has said it with Anonymous.
"We neither condemn nor applaud these attacks," spokesman Kristinn Hrafnsson said, referring to the moves against MasterCard and other sites. "We believe they are a reflection of public opinion on the actions of the targets."
WikiLeaks has reported repeated attacks on its computer systems over the last few weeks by unknown assailants. Earlier the group attributed the cyber attacks to the intelligence agencies of the United States and its allies - although Pentagon spokesman Col. David Lapan said he had "no information to suggest the Defense Department has knowledge" of the attacks on WikiLeaks.
Anonymous and its sympathizers are using a modified version of software generally used to conduct "stress testing" on websites, according to Paul Mutton, an analyst with London-based internet research and security company Netcraft, which is tracking the attacks.
The technique allows even unsophisticated supporters to participate in attacks because all they have to do is download the file, which is then remotely operated to send a stream of bogus page requests to target websites.
Mutton said the number of computers spewing out spam had jumped from 400 to 2,000 machines on Wednesday - relatively small numbers, he said, but still apparently enough to overwhelm MasterCard's main page for several hours.
"I've been surprised at how effective its been," he said. "You don't need huge numbers of people to carry out an attack like that."
Offline, some efforts by the U.S. government and its allies to punish the website dedicated to publishing secret documents landed in court or headed to one. Judicial authorities in France foiled the French government's effort to boot WikiLeaks from its French computer servers, while supporters in Switzerland and Germany threatened lawsuits against U.S. financial companies who have cut their ties to WikiLeaks.
A protest in Australia - the first of a series planned there and in Britain - sent about 250 demonstrators into the streets of Brisbane.
"Over the last few weeks, we've seen a worldwide campaign against WikiLeaks and its project to create more transparency within government," rally organizer Jessica Payne said. "We're here today to defend WikiLeaks and defend our right to freedom of information."
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WikiLeaks has been under intense pressure since it began publishing some 250,000 U.S. State Department cables, with attacks on its websites and threats against its founder, Julian Assange, who is now in a British jail fighting extradition to Sweden on sex crime allegations.
U.S. officials say WikiLeaks' actions have thrown diplomacy worldwide into disarray, caused countries to curtail their dealings with America and, in the case of an earlier release of classified military documents, put the lives of informants at risk.
Top U.N. human rights official Navi Pillay told reporters in Geneva that she was concerned that moves against WikiLeaks "could be interpreted as an attempt to censor the publication of information" in a way that violates WikiLeaks' right to free expression.
Meanwhile WikiLeaks' financial facilitators said they were sharpening their legal knives.
The Germany-based Wau Holland Foundation, which has previously described itself as WikiLeaks' main backer, on Thursday protested PayPal's decision to cut ties with WikiLeaks and said about $13,000 in donations for WikiLeaks had been frozen in the company's account.
The foundation rejected PayPal's allegation it was supporting illegal activity and said its lawyer had demanded that PayPal restore access to the account.
WikiLeaks' payment processor, DataCell ehf, said it was preparing to sue Visa and MasterCard over their refusal to process donations to WikiLeaks. DataCell CEO Andreas Fink said he would seek damages from the U.S. credit card companies over their decision to block WikiLeaks funds, saying "it is simply ridiculous to think WikiLeaks has done anything criminal."
He said he had been told that credit card donations to WikiLeaks would be frozen at least until next week.
MasterCard has declined repeated requests for comment on why they suspended WikiLeaks.
Visa Europe Ltd. spokesman Simon Kleine said organizations could receive funds through Visa so long as they were legal and didn't breach the company's operating rules. But he said when issues arose "we need to ensure that they're in compliance with our operating rules and in compliance with local laws."
He declined to say what those issues were in WikiLeaks' case. "We investigate on a commercially confidential basis," he said, denying allegations the company had folded under U.S. pressure.
PayPal's Vice President Osama Bedie acknowledged that his company cut ties after seeing a U.S. government letter that said WikiLeaks' activities in the U.S. were illegal.
Another pro-WikiLeaks rally was planned in Brisbane on Friday, and similar protest was being held Monday in London outside the Swedish Embassy.
In the central Pakistani city of Multan, dozens of people took to the streets to burn U.S. and British flags to protest Assange's detention. Organizer Tariq Naeemullah called for the Australian's immediate release.
"The brave man was arrested because he was exposing the real face of the big powers," he said.
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