The FBI has identified the probable culprit behind last week_s Internet attacks, security experts said Monday.

While the FBI remains tight-lipped about its investigation, Stanford University system-software developer David Brumley -- who has taken an active role in the search -- said, "It_s just a matter of time now." Brumley said the suspect is believed to live in the United States, and is not connected to the hacker known as "mafiaboy," who captured the attention of investigators and reporters early Monday when he appeared to boastfully take credit on IRC chats. "There are lots of people on IRC right now trying to take credit for the attacks," said Brumley. "We don_ believe “mafiaboy” was involved in the major attacks." Brumley declined to reveal the nickname of their chief suspect, but said he expects an arrest soon. "We_ve given the FBI five different pieces of evidence," he said. "We_ve had this guy in mind for awhile, probably since last Wednesday, but it never hurts to have another pair of eyes. They_re being extra careful." Not everyone agrees that the Feds have found their man, however.