FBI has launched a worldwide crackdown on a notorious denial-of-service attack. It executed more than 40 search warrants against people in the United States believed to be part of a group calling itself Anonymous. The group claims it launched the cyber attacks as protests against large corporations. In a coordinated move, the U.K.'s Metropolitan Police also served search warrants and arrested five people. The FBI says authorities in the Netherlands, Germany, and France are cooperating in the investigation of Anonymous.

Anonymous, a loose-knit collection of activists, has claimed responsibility for attacking the websites of companies such as Visa, Mastercard and Paypal, all of whom severed their links with WikiLeaks after it began publishing its massive trove of secret U.S. diplomatic memos.

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