The only clue seems to be the name of the malware in the screenshot. Intego's blog post is sparse on details, but one thing that they haven't explored is which antivirus engine Apple might be using behind the scenes.
The following screenshot is alleged to show a system warning after downloading malware via Safari:
I just noticed a very intriguing post on Intego's Mac Security Blog claiming that Apple's upcoming operating system, Mac OS X v10.6 'Snow Leopard,' will have built-in antivirus functionality.
