The MacBook Air went first; a tiny Fujitsu laptop running Vista was hacked on the last day of the contest; but it was Linux, running on a Sony Vaio, that remained undefeated as conference organizers ended a three-way computer hacking challenge Friday at the CanSecWest conference.

Earlier this week, contest sponsors had put three laptops up for grabs to anyone who could hack into one of the systems and run their own software. A US$20,000 cash prize sweetened the deal, but the payout was halved each day as contest rules were relaxed and it became easier to penetrate the computers.

On day two, Independent Security Evaluators' Charlie Miller took the Mac after hitting it with a still-undisclosed exploit that targeted the Safari Web browser. After about two minutes work, Thursday, Miller took home $10,000, courtesy of 3Com's TippingPoint division, in addition to his new laptop.

It took two days of work, but Shane Macaulay, finally cracked the Vista box on Friday, with a little help from his friends.

Macaulay, who was a co-winner of last year's hacking contest, needed a few hacking tricks courtesy of VMware researcher Alexander Sotirov to make his bug work. That's because Macaulay hadn't been expecting to attack the Service Pack 1 version of Vista, which comes with additional security measures. He also got a little help from co-worker Derek Callaway.

Under contest rules, Macaulay and Miller aren't allowed to divulge specific details about their bugs until they are patched, but Macaulay said the flaw that he exploited was a cross-platform bug that took advantage of Java to circumvent Vista's security.

"The flaw is in something else, but the inherent nature of Java allowed us to get around the protections that Microsoft had in place," he said in an interview shortly after he claimed his prize Friday. "This could affect Linux or Mac OS X."

Macaulay said he chose to work on Vista because he had done contract work for Microsoft in the past and was more familiar with its products.

Although several attendees tried to crack the Linux box, nobody could pull it off, said Terri Forslof, a manager of security response with TippingPoint. "I was surprised that it didn't go," she said.

Some of the show's 400 attendees had found bugs in the Linux operating system, she said, but many of them didn't want to put the work into developing the exploit code that would be required to win the contest.

Earlier, Miller said that he chose to hack the Mac because he thought it would be easiest target. Vista hacker Macaulay didn't dispute that assertion: "I think it might be," he said.