Anonymous is not so anonymous any more. The computer hackers, chat room denizens and young people who comprise the loosely affiliated internet collective have increasingly turned to questionable tactics, drawing the attention of the FBI, the Department of Homeland Security and other federal investigators.

What was once a small group of pranksters has become a potential national security threat, federal officials said.

The FBI has carried out more than 75 raids and arrested 16 people this year in connection with illegal hacking jobs claimed by Anonymous. Since June, the Department of Homeland Security has issued three "bulletins" warning cyber-security professionals of hacking successes and future threats by Anonymous and related groups, including a call to physically occupy Manhattan's Wall Street on Sept. 17 in protest of various US government policies.