Microsoft's admitted that it, too, was recently hit by hackers using the same techniques as recent attacks on Facebook and Apple, but says that no customer data has been compromised.
In an announcement slipped out late on Friday night, the company says it chose not to reveal the breach until it had investigated fully.
"During our investigation, we found a small number of computers, including some in our Mac business unit, that were infected by malicious software using techniques similar to those documented by other organizations," says Matt Thomlinson, Microsoft's general manager for trustworthy computing security, in a blog post.
"We have no evidence of customer data being affected and our investigation is ongoing."
The attack exploited the same zero-day Java vulnerability which was recently spread through a website for software developers to attack Apple and Facebook. The source of the attacks isn't clear, although the usual suspects - the Chinese government and Eastern European criminals - have been suggested.
"If you haven't already done so, patch your computers and consider running anti-virus software on your Macs as well as your PCs," says graham Cluley of security firm Sophos.
"Clearly some of the bad guys are targeting Mac OS X, knowing that many 'cool' developers prefer to write their software on shiny Apple hardware as well as dull beige PCs."