The FBI executed more than 40 search warrants today in connection with its investigation into Operation Payback, last month's wave of cyber attacks targeting companies that cut off Wikileaks. Things are not looking good for Anonymous.

Last month, The loose-knit hacking collective Anonymous retaliated against Visa, Mastercard and Paypal for cutting ties with Wikileaks, hitting their websites with distributed denial of service attacks—floods of traffic that overwhelmed their servers. Authorities have since launched a globe-spanning investigation, including a raid on a Texas server farm suspected of hosting Anonymous chat rooms, and the arrests today in the UK of five suspected Anonymous members, aged 15-25. (There were no arrests in the U.S.)

A guy claiming to be at the receiving end of one of the American raids, Georgia Tech freshman Zhiwei Chen, posted a copy of the warrant, and the business card of the FBI agent who served it, to Reddit. He writes: "They came in the dorm room bustin in @ 7:00, and pushed everyone out of bed. They searched the place and questioned all people involved." (Click to Enlarge)

Chen says he's a former administrator of the Operation Payback chat room, where most of the planning occurred.

Anonymous released a statement today in relation to the UK raids, calling them a "serious declaration of war." "Arresting somebody for taking part in a DDoS attack is exactly like arresting somebody for attending a peaceful demonstration in their hometown," the press release reads.

But Anonymous is clearly hurting, even as members continue to organize in support of the protests in Tunisia and Egypt. "Subdued" is how the Financial Times describes the mood in Anonymous chat rooms. "We lost a lot of our brothers today," wrote one user in the "Operation Payback" channel today.

The collective's greatest strength lies in the fact that any moderately-savvy Joe Internet User can hop into a public Anonymous chat room, download a push-button program, and join a DDoS attack. Thousands of small clicks add up to outsized results (and media coverage.) But even though they inflict no lasting damage, DDoS is a crime—punishable by 10 years imprisonment, according to the feds!—and Anonymous' inclusiveness makes it easy for the authorities to spy on every move: Imagine a gang of diamond thieves plastering the Internet with slick advertisements for a new heist, inviting anyone to participate, no questions asked.

If there's ever another Operation Payback, Anonymous might need to figure out how to be a bit more anonymous.

[Image of Anonymous member at pro-Wikileaks rally via Takver's Flickr]