According to antivirus vendor Sophos, Apple this week, in an undocumented move, tweaked its OS X malware defenses.

In particular, OS X 10.6.4 now provides better protection against a Trojan application called HellRTS, aka Pinhead-B, which has been turning up in fake iPhoto software being circulated by attackers.

"This Trojan can give hackers the green light to send spam e-mail from your computer, take screenshots of what you are doing, access your files and clipboard, and much, much more," said Graham Cluley, senior technology consultant at Sophos, in a statement. "But what's curious to me is why Apple didn't announce they were making this update in the release notes or security advisory that came with Mac OS X 10.6.4. It's almost as if they don't want to acknowledge that there could be a malware threat on Mac OS X."

Despite the existence of HellRTS, which first hit the scene in April, and is a variant of a Trojan first seen in 2004, is there really a clear and present malware threat to Apple's OS X?

Late last year, Symantec predicted that the amount of malware aimed at Mac OS X would continue to increase. In its report predicting security trends for 2010, Symantec wrote: "In 2009, we saw Macs and smartphones targeted more by malware authors, for example the Sexy Space botnet aimed at the Symbian mobile device operating system and the OSX.Iservice Trojan targeting Mac users. As Mac and smartphones continue to increase in popularity in 2010, more attackers will devote time to creating malware to exploit these devices."

But if the primary, if not sole, impetus for creating malware is to steal people's personal information for financial gain -- typically by selling that information to others or using purloined credentials to literally steal cash -- is an operating system with roughly 5% market share screaming "hack me" to potential attackers?

"It's true to say that there are far, far fewer malware threats for Mac than there are for Windows -- but that doesn't mean the problem is non-existent. Unfortunately, many Mac users seem oblivious to security threats which can run on their computers, even though Apple has now built in some elementary protection," said Cluley. "This lack of awareness isn't helped when Apple issues an anti-malware security update by stealth, rather than informing the public what it has done."

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