Calling the FBI raids a "widespread phenomenon," John Vranesevich said the FBI raided hackers in New York, New Jersey, Texas, Washington and California.
Vranesevich is the founder of a Web site called AntiOnline.com, which is dedicated to educating the public about computer security issues.
Although the FBI in Washington declined comment Monday, it confirmed that four search warrants were executed last week in Texas in connection with an investigation into allegations of computer intrusion, including one search at the home of a prominent hacker in Houston.
These federal raids come as hackers continue to attack federal Web sites, forcing them to shut down and become inaccessible to the public.
Computer hackers vandalized two more government sites on the Internet Monday and left a taunting note promising to attack more federal computers because of the ongoing FBI investigations.
Hackers from different organizations defaced a Web page early Monday within the Interior Department and a site run by a federal supercomputer laboratory in Idaho Falls, Idaho, claiming "it's our turn to hit them where it hurts."
On the Interior Department's Web page, the hackersÂ' message said, "Now, it's our turn to hit them where it hurts by going after every computer on the Net with a .gov (suffix). We'll keep hitting them until they get down on their knees and beg."
At the site maintained by the Idaho National Engineering and Environmental Laboratory, a note threatened the electronic destruction of the powerful computers that "serve" pages on the Internet "if the FBI doesn't stop."
"We could have done worse, like destroying completely all servers," the note said. "We can do it if we want, but hackers are waiting for Justice."
Referring to these messages left behind by the hackers, Vranesevich said recent hack attacks were in response to the FBIÂ's hacker "witch hunt."
He said the FBI probably began its crackdown after a group calling itself "Global Hell" broke into the White House web site in early May.
Last week, hackers claiming to be from a group called "MOD" Â— Masters Of Downloading Â— defaced the U.S. Senate web site, causing it to be taken offline until the weekend.
The FBI also was forced to take down its own Internet site last week after hackers launched an electronic attack against it. It remained inaccessible Monday, along with the Web site for its National Infrastructure Protection Center, which helps investigate computer crimes.
Despite the close timing of the attacks, Vranesevich said they were not orchestrated and that a virtual turf war has begun among thee individual hacking groups, in which hey make fun of each other and try to "one-up" each other during hack attacks.
"MOD" Wednesday made fun of "Global Hell" for their attacand "F0rPaxe"Â— a group of Portuguese hackers known for hacking Army and Air Force servers who attacked the Interior Department Â— made fun of "MOD" for making fun of "Global Hell."
Vranesevich said hackers attack these Web sites "because they can." He said they use software that scans for computers in a particular range that are vulnerable to attack.
By Lee Kaplan