The Mac operating system benefits from the legacy of its Unix (BSD) heritage, in that Unix has always been developed as a multi-user system for network environments and therefore enforced a rigid internal security model, compared to the then-burgeoning single user / single system home computer operating systems. However, it's also true that the principle of "security through obscurity" has benefit Macs for years, and that benefit is waning as they become a broader target. I don't know if it's still the case (probably not), but for a while Sun's Java virtual machine for OS X had continuous 'root' access which represents a potential avenue for intrusion. One hole like that gets closed and others are found. All it really takes is the desire, wherewithal, and opportunity. It's the eternal battle between arms and armor.
