For Mac owners, the alarming news just keeps coming. Two weeks after the Flashback trojan infected hundreds of thousands of Apple-branded computers, a new, more devious strain is being reported. Flashback.S, as the new variant of the Java-exploiting malware is called, is even more subtle than its predecessor and thus can find its way onto users' machines more quietly. Suddenly, Mac users find themselves considering whether or not to install antivirus software.

To even ask such a question would be unthinkable among Windows customers, who for years have been the main targets of hackers and cyber criminals. Microsoft's desktop operating system still dominates Mac OS X in market share, but Apple is selling more and more devices each quarter. While the bulk of its revenue now comes from iPhones and iPads, the company's laptops and desktops have become more popular over time.

Malware on Macs is nothing new. In the 1980s, simple viruses would spread among early Apple machines via floppy disk, and later by CD-ROM. Twenty years later, the first known virus targeting Mac OS X surfaced.

For the most part, the history of Mac malware has been relatively uneventful, with many of the exploits being proofs-of-concept or simple gags that display a graphic or a few lines of text to the user. However, in recent years, things have gotten more serious.

Mac Malware Comes of Age, But Remains a Minor Threat

Last year, the Mac Defender trojan started infecting users' machines, in some cases leaking sensitive personal information to third parties. It was perhaps the most well-known Mac security issue of 2011, which saw an uptick in malware directed at Apple's computers.

In 2012, the threats seem to keep piling up. Yet in the grand scheme of things, Mac malware is still tiny compared to what infects Windows machines worldwide.

The latest Mac exploits have received a lot of press attention, but that's largely because of their unique nature. Windows vulnerabilities don't grab headlines every time they appear, simply because they've been common on the world's most widely used operating system for years.

Whereas running antivirus software is a no-brainer for Windows users, those on Mac OS X still have the luxury of being picky, as long as they're exercising the utmost care and day-to-day common sense. In addition to safe browsing and email habits, using tools like FlashbackChecker to scan for common pieces of Mac malware is well worth the effort.

It's probably not quite time to panic for Mac users who can play it safe. But that isn't to say this couldn't change. Windows remains dominant, but Mac OS X is gaining in market share, and at least one security expert believes that Apple's desktop operating system is about a decade behind Windows in terms of security. And if there's any merit to the theory that Windows' ubiquity makes it a vulnerable target, we should probably expect to see an uptick in iOS-specific malware in the future, as iPhones and iPads fly off the shelves quarter after quarter.