An Internet outlaw's decision to go to work for the FBI poured light on a secretive world where young computer experts caused havoc and where authorities say a Chicago man and others celebrated their successes as they stole hundreds of thousands of dollars with stolen credit card numbers.

Court documents unsealed Tuesday revealed charges against six individuals in Europe and the United States and showed the clash between law enforcement and Internet hackers, a group of worldwide computer enthusiasts already threatening to retaliate.

Law enforcement officials said it marked the first time core members of the loosely organized worldwide hacking group Anonymous have been identified and charged in the U.S.

Some Anonymous members put on a brave face.

"Anonymous is a hydra, cut off one head and we grow two back," read one defiant message posted to Twitter.

At the center was the legendary hacker known as "Sabu," who when he was arrested last June was identified as Hector Xavier Monsegur, 28, a self-taught, unemployed computer programmer with no college education. Authorities said his cooperation has helped to prevent more than 300 Internet attacks.

Authorities said he was living on welfare in public housing in New York as he carried out crimes that made him a hero to some in cyberspace until he made a rookie mistake — he posted something online without cloaking his IP address, or computer identity — and someone tipped off the FBI.