“On Halloween, professional Ukranian online criminals were found using Trojan-horse software to target, for the first time, computers running Apple’s OS X operating system — just as they have been doing for years on the more ubiquitous flavors of Windows.” Wired news.
This on the surface sounds like the first of what could be a flood of Windows type security concerns on the Mac. It is however an example of how the Mac is a very different beast when it comes to this type of exploit.
Firstly one must be looking for porn online, then one must see the link for a new Quicktime codec and download the dmg. One must then double click to mount the disc image and install the application. Also you need to type in your admin password as you do for all new apps.
Once installed, the Trojan hijacks the system’s domain-name service. Internet-connected applications use DNS to translate the domain part of an URL, such as www.Wired.com, into the numeric IP address of a server. By hijacking the DNS, the attacker is able to replace search results with links to sites that he controls, in hopes of making money from online purchases.

Now this sounds like a security issue but it is more an issue for users to be aware of, not a security flaw that Apple can do anything to fix. So be warned, security is mostly a user issue not an OS problem. OSX has always been as secure as could be managed but until now Mac users have not been targeted specifically and this is an attack on users not the operating system.