In many APT attacks, the hackers first break into social media accounts belonging to friends of their victims. They mine them for information, and then use these accounts to send very realistic looking messages to people working within the company they want to hit. If they can trick an employee into downloading software or visiting a website laden with attack code, they can get a foothold in the network.

It's the next step -- moving around the network and getting access to corporate secrets -- that's tricky. And that's where Apple is at a disadvantage, according to the iSec research.

Mac users have been pretty well insulated from APT attacks to date. Rob Lee, a director with computer investigations firm Mandiant says he's never seen a Mac compromised during his investigations. They simply aren't targets because they aren't widely used in the enterprise customers that Mandiant typically investigates, he said Wednesday. In fact, when a customer comes to Mandiant after its been hacked, Lee often recommends that executives go out and buy a Macintosh so that they can continue to do company business with less risk of re-infection.

Security experts at Black Hat this week agree that these targeted hacking attacks are unparalleled and extremely widespread. On Tuesday, McAfee saying that it had uncovered evidence of a sophisticated hacking operation that had broken into systems at more than 70 companies over the past five years.

"I am convinced that every company in every conceivable industry with significant size and valuable intellectual property and trade secrets has been compromised (or will be shortly), with the great majority of the victims rarely discovering the intrusion," wrote Dmitri Alperovitch, McAfee's vice president of threat research in a