There was one defect in the Safari browser that allowed this. It was quickly fixed. In practice, the spyware/virus problem on Mac is almost nonexistent. Believe me, I've used every version of Windows since 3.1, and every version of MacOS and OS X. There is simply no way Windows can compare to the worry-free robustness of OS X.
-ccm
The time to hack the Mac was 2 minutes... because that's how long it took to get the referees to navigate the computer to the pre-prepared website.
Charles Miler, the winner of the MacBook Air and $10,000 told interviewers that he, along with his team of two ex-NSA computer security experts, worked three weeks in advance of the CanSec West conference where the contest was held, to find the security hole in Mac OSX.
Vista was hacked six hours later but the team who did it had not done any advance preparation.
The LINUX laptop was not compromised, even on the third day of the contest.