The security researcher who walked away with US$10,000 last week by hacking a MacBook Air in less than two minutes said he chose to attack Apple's operating system for one simple reason.

"It was the easiest one of the three," said Charlie Miller, a principal analyst with Independent Security Evaluators (ISE), a US-based security consultancy. "We wanted to spend as little time as possible coming up with an exploit, so we picked Mac OS X."

Last Thursday afternoon, Miller breached a MacBook Air, one of three laptops up for grabs in the "PWN To OWN" hacker challenge at CanSecWest, a security conference in Canada. For his efforts, he was got the computer and a US$10,000 cash prize.

The MacBook Air was running the most current version of Mac OS X, 10.5.2, with all the latest security patches applied. The other two computers, a Sony Vaio VGN-TZ37CN running Ubuntu 7.10 and a Fujitsu U810 notebook running Windows Vista Ultimate SP1, were also up-to-date and fully patched.

"We sat down about three weeks ago and decided we wanted to throw our hats into the ring," said Miller, referring to himself and ISE colleagues. "It took us a couple of days to find something, then the rest of the week to work up an exploit and test it.

"It took us maybe a week altogether," Miller said.

Because Miller was bound by a non-disclosure agreement with 3Com's TippingPoint, the security company that ponied up PWN To OWN's cash prizes, he was unable to share details of the vulnerability. He did confirm, however, that he had exploited a bug in Safari 3.1, the current version of Apple's browser.

The PWN To OWN challenge actually started Wednesday, but the rules for that first day required researchers to break into one of laptops using a remote code-execution exploit of a zero-day. At stake: the laptop and US$20,000. Only one researcher stepped up that day, however, and was unsuccessful.

The computers' exposure to attack was expanded by allowing hackers to go after any client-side applications installed by default, including Web browsers. Contestants were also allowed to replicate the common tactic of duping a user into following a link in an e-mail or visiting a malicious Web site. In Miller's case, he had set up a malicious Web site; the URL to that site was typed into Safari's address bar.