A collective of hackers claiming to belong to the group Anonymous defaced a security firm’s home page in an apparent retaliation for the Tuesday arrests of five alleged Anonymous members.

The hackers posted a rant on the Web site of the Spanish security firm PandaLabs, which Anonymous accused of having worked with the FBI to help arrest 25 members of the group last month. The hackers also posted dozens of PandaLabs staff e-mails and passwords. Computerworld suggests PandaLabs may have also been targeted because the company’s technical director, Luis Corrons, had previously posted a blog praising the five arrests on Tuesday.

The Washington Post’s Ellen Nakashima, Peter Finn and Sari Horwitz reported Tuesday that five alleged members of Anonymous, a notorious hacking group, were charged after a key member of the network, New York-based Hector Xavier Monsegur, began secretly working with the FBI last year.

Monsegur, who was known by the online handle Sabu, was known for launching Twitter campaigns inciting users to crash government Web sites by overwhelming their servers , according to one former Anonymous member. He was caught when he failed to mask his Internet protocol address on one occasion, and pleaded guilty in August to 12 hacking charges and faces up to 124 years in prison, according to Computerworld.

Monsegur began cooperating with prosecutors with the hope of receiving a shortened prison sentence, officials said.

The message on the PandaLabs site, posted alongside a YouTube video showing past Anonymous hacks, read:

“Yeah yeah we know. . .Sabu snitched on us as usually happens FBI menaced him to take his sons away we understand, but we were your family too (remember what you liked to say?) It’s sad and we cant imagine how it feels having to look at the mirror each morning and see there the guy who shopped their friends to police.”

The statement references Sabu’s habit of referring to Anonymous hacktivists as his “brothers.”

PandaLabs’ Web site was still unavailable as of 9:30 a.m. Wednesday.

Those arrested Tuesday were alleged members of the group LulzSec, an offshoot of Anonymous. “Federal prosecutors in New York charged five men — two from Britain, two from Ireland and one from Chicago — in connection with a string of cyber-assaults in which hackers stole confidential information from U.S. companies and temporarily shut down government Web sites,” The Post reported.

In one recent case, the group allegedly provided e-mails from private intelligence firm Stratfor to WikiLeaks, which published the documents in February.

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