The latest Mac OS update from Apple contained dozens of security fixes, including the now much criticized out-of-date Flash Player. Now Mac anti-virus firm Intego has identified additional malware detection in the system’s definitions that identifies the HellRTS backdoor malware trojan.

The company said back in April that this trojan allows hackers to open a backdoor into a system which then permits hackers to install malware for a number of scams.

Over at security vendor Sophos, which calls the trjoan OSX/Pinhead-B, the company’s researchers also identified the new anti-malware protection within the Mac OS X update.

Graham Cluley, a senior technology consultant at Sophos, said it was encouraging to see Apple provide detection ability in the new release.

"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”, he said in a blog posting. “It's almost as if they don't want to acknowledge that there could be a malware threat on Mac OS X."

“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," continued 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."

Apple did not return a requests for comment.