Apple Issues Stealth Trojan Update

According to Computerworld, Sophos claims that Apple's OS X 10.6.4 upgrade secretly patched XProtect.plist, a file that contains elementary signatures of a handful of Mac threats, so that it now scans for a Trojan that Symantec labels as "HellRTS." The Inquirer reports that the Trojan disguises itself as Apple’s popular iPhoto application.It can allow remote hackers to gain control over Mac computers and any sensitive personal data on them.

PCWorld.com notes that Sophos' Graham Cluley is curious why Apple decided to issue this stealth update. He suspects it has to do with marketing:

Unfortunately, many Mac users seem oblivious to security threats which can run on their computers. And that isn't helped when Apple issues an anti-malware security update like this by stealth, rather than informing the public what it has done. You have to wonder whether their keeping quiet about an anti-malware security update like this was for marketing reasons. 'Shh! Don't tell folks that we have to protect against malware on Mac OS X!'