Many of the malicious programs found in that analysis, not surprisingly, are Windows-specific attacks that Mac users are getting inadvertently. Perhaps by visiting infected Web sites and having the malware dropped into their browser caches, opening e-mail attachments, or by sharing and copying files by USB drives and other means.
Some of the malware are cross platform attacks, based on Java, while a few are Mac specific. From Sophos' blog late last week:
You'll also notice a lot of Java-based attacks in the list, these are obviously cross-platform and may have been found in internet caches by users who were hit by a drive-by attack. Many of these might have been designed to download further Windows-based attacks to computers, but they could easily be adapted to download Mac-based threats too.
You'll also see some Mac OS X-specific malware in there (OSX/Jahlav and DNS Changer). These are well known Mac Trojans that are typically disguised by hackers on BitTorrent sites, or planted on websites as alluring downloads or plugins to view videos.
Does this mean Mac users should rush out and install anti-virus software on their systems? Probably not. That is unless they are undertaking known risky activities such as visiting BitTorrents and downloading or viewing questionable software.
That means anti-virus software today is still a choice Mac users have to make, balancing risk and convenience. However, as Mac-based viruses grow in complexity, numbers, and efficiency - it's a luxury that may be lost soon.
The only caveat I'd have to that is that if your Mac is on a local network, your local users could be placing you at increased risk. So keep that in mind.
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