SAN FRANCISCO (AP) – Anonymous is not so anonymous anymore.

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 say.

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 U.S. government policies.

San Francisco police arrested more than 40 protesters last month during a rowdy demonstration organized by Anonymous that disrupted the evening commute. The group called for the demonstration after the Bay Area Rapid Transit system shut off it cell service in San Francisco stations to quell a planned protest over police shooting on a subway platform.

“Anonymous’ activities increased throughout 2011 with a number of high-profile attacks targeting both public and private sector entities,” one of the bulletins issued last month said.