An online news site published and then retracted a story this week that claimed a radical Islamic group was behind a virus-like attack in January that clogged the Internet.

In Wednesday's article on the Web site of Computerworld magazine, someone identified as "Abu Mujahid" said his Pakistan-based Harkat-ul-Mujahadeen group had unleashed the Internet worm attack as part of a "cyber jihad."

Mujahid was really Brian McWilliams, 43, a freelance journalist in Durham, N.H. McWilliams said he duped the writer, Dan Verton, because he wanted to teach reporters "to be more skeptical of people who claim they're involved in cyberterrorism."

Three hours after Verton's story appeared, Computerworld removed it from the Web site because of "questions about its authenticity," Editor-in-Chief Maryfran Johnson said. The trade magazine is based in Framingham, Mass., and published by International Data Group.

On Thursday, Computerworld published a new story by Verton titled "Journalist perpetrates online terror hoax."

Verton, a former Marine intelligence analyst who frequently reports on computer security, said he based the original story on an e-mail interview. He said he fell victim to "an elaborate scheme to dupe security companies and journalists."

"I feel like I've been had, and that's never an easy thing to swallow," Verton wrote. "So, I'm left here scratching fleas as the price you sometimes pay for sleeping with dogs."

Traditional journalism ethics dictate that reporters don't misrepresent their identities. McWilliams defended the technique, saying it was "in the grand tradition of undercover reporting."

McWilliams said he registered the Internet domain name harkatulmujahideen.org to attract correspondence from Muslim radicals, planning to use messages received as story fodder.

McWilliams said he left a mirrored version of the Web site on a server in Pakistan, and even sought to boost its authenticity by defacing it in an effort to make it appear that pro-U.S. hackers had attacked the site.

Verton said the hoax was convincing enough that his calls to the FBI's National Infrastructure Protection Center turned up no clues to its inauthenticity. But Johnson said a friend told her McWilliams was bragging on an e-mail list about having tricked Computerworld.

McWilliams said Verton and Computerworld should have checked the Web site's registry or his e-mail header information. Had they done so, they would have learned that Abu Mujahid was in the United States, not Pakistan.

McWilliams said he regrets letting the scheme progress to the point of publication.

"I wanted to see whether he'd go the extra mile to see who he's dealing with," McWilliams said of Verton. "I would've at least asked for a phone number. He didn't ask for any sort of corroboration."

Experts have been unable to trace the origin of the so-called Slammer worm and say they have no evidence terrorism was involved.