London:
In a campaign that had some declaring the start of a "cyberwar," hundreds of Internet activists mounted retaliatory attacks on Wednesday on the Web sites of multinational companies and other organizations they deemed hostile to the WikiLeaks antisecrecy organization and its jailed founder, Julian Assange.
Within 12 hours of a British judge's decision on Tuesday to deny Mr. Assange bail in a Swedish extradition case, attacks on the Web sites of WikiLeaks's "enemies," as defined by the organization's impassioned supporters around the world, caused several corporate Web sites to become unavailable or slow down markedly.
Targets of the attacks included the Web site of MasterCard, which had stopped processing donations for WikiLeaks; Amazon.com, which revoked the use of its computer servers; and the online payment service PayPal, which stopped accepting donations for Mr. Assange's group. Visa.com was also affected by the attacks, as was the Web site of the Swedish prosecutor's office and the lawyer representing the two women whose allegations of sexual misconduct are the basis of Sweden's extradition bid.
The Internet assaults underlined the growing reach of self-described "cyberanarchists," antigovernment and anticorporate activists who have made an icon of Mr. Assange, whom they consider one of their own.
The attacks also appeared to show renewed support for Mr. Assange, a 39-year-old Australian, who has appeared increasingly isolated in recent months amid the furor stoked by WikiLeaks's Web site posting of hundreds of thousands of secret Pentagon documents on the wars in Afghanistan and Iraq. Even some of his closest associates abandoned him during the turmoil .
Mr. Assange has come under renewed attack in the past two weeks for posting the first tranche of a trove of 250,000 secret State Department cables that have exposed American diplomats' frank assessments of relations with many countries, forcing Secretary of State Hillary Rodham Clinton to express regret to world leaders and raising fears that they and other sources would become more reticent.
Mr. Assange has been simultaneously fighting a remote battle with the Swedish prosecutors, who have sought his extradition for questioning on accusations of "rape, sexual molestation and forceful coercion" made by the Swedish women. Mr. Assange has denied any wrongdoing in the cases.
American officials have repeatedly said that they are reviewing possible criminal charges against Mr. Assange, raising the possibility of his having to fight for his freedom on two fronts. The New York Times and four other news organizations last week began publishing articles based on the archive of cables made available to them.
The cyberattacks in Mr. Assange's defense appear to have been coordinated by Anonymous, a loosely affiliated group of activist computer hackers who have singled out other groups before, including the Church of Scientology. Last weekend, members of Anonymous vowed in two online manifestos to take revenge on any organization that lined up against WikiLeaks.
Anonymous claimed responsibility for the MasterCard attack in Web messages and, according to one activist associated with the group, continued to conduct multiple and repeated waves of attacks on MasterCard and other companies during the day.
The activist, Gregg Housh, who disavows any personal role in any illegal online activity, said in a telephone interview that 1,500 supporters had been in online forums and chat rooms organizing mass "denial of service" attacks on some of the companies. His account was confirmed by Jose Nazario, a senior security researcher at Arbor Networks, a Chelmsford, Mass., firm that tracks malicious activity on computer networks.
Almost all the corporate Web sites that were attacked appeared to be operating normally later on Wednesday, suggesting that any economic impact was limited. But the sense of an Internet war was reinforced when Netcraft, a British Internet monitoring firm, reported that the Web site being used by the hackers to distribute denial-of-service software had been suspended by a Dutch hosting firm, Leaseweb.
In a denial of service attack, many computers are harnessed together to transmit streams of data packets at a target computer, overwhelming its ability to process the incoming data.
A sense of the belligerent mood among activists associated with the Anonymous group was given when one contributor to a forum the group uses, WhyWeProtest.net, wrote of the attacks: "The war is on. And everyone ought to spend some time thinking about it, discussing it with others, preparing yourselves so you know how to act if something compels you to make a decision. Be very careful not to err on the side of inaction."
Mr. Housh acknowledged that there had been online talk among the hackers of an Internet campaign against the two Swedish women who have been Mr. Assange's accusers in the Swedish extradition case, but he said that the issue remained "touchy" and that "a lot of people don't want to be involved."
A Web search showed new blog posts in recent days in which the two women, identified by the Swedish prosecutors only as Ms. A. and Ms. W., were named, but it was not clear whether there was any link to Anonymous, or to a concerted campaign of any kind. Previous posts naming the two women appeared on Web sites supporting Mr. Assange a few days after their accusations surfaced in late August.
The attacks were seen by many supporting them online as a counterstrike against the United States. Mr. Assange's online supporters have widely condemned the United States as the unseen hand coordinating efforts to choke off WikiLeaks by denying it financing and suppressing its network of computer servers.
Borrowing from the lexicon favored by Mr. Assange, who has depicted WikiLeaks's efforts as part of a millennial struggle to free the world from entrenched elites, many of the computer activists backing the online attacks have spoken of him as standing on "the front line" of a struggle pitting a vast if amorphous WikiLeaks following against the United States.
Mr. Housh, an American activist, described Mr. Assange in an interview as "a political prisoner," a common view among WikiLeaks supporters who have joined Mr. Assange in condemning the Swedish accusations of sexual abuse as part of an American-inspired "smear campaign" to discredit him and WikiLeaks.
Another activist used the analogy of the civil rights struggle.
"This is the modern equivalent of a lunch counter sit-in," a contributor using the name Moryath wrote in a comment on the slashdot.org technology Web site. "Are they "disrupting business? Perhaps, but no worse than the lunch counter sit-ins did."