Not that it can't attack it. It can attack anything. Mac's are safe as they do not have the security breach that the worm is designed to hunt for. It is only on machines that use windows and use IE for a browser.
So far, Mac computers are relatively safe from viruses and worms and trojans as those things are designed for windows operating systems. No one has gotten to the point of developing a vicious intruder for the mac...yet !
To be honest bout this....Belive it or Not Time....
Most worms and viruses are actually designed by the same people that build the operating systems or are hired to hunt for vulnerabilities and these people design the worms and trojans to sniff out loopholes in the system and security to exploit the operating system.
Once a worm is designed it is sent to testing organizations (computer tech schools) to be ran multiple times and altered to test for any issues.
It is at this point that things go bad...the test is either stolen and altered by devious minds or it is accidentally lost and subsequently found in the hands of script kiddies and gamesters that think it is cool to infect someone else's computer. It then escalates into something wild as hackers begin to use the program to infiltrate other computers and it is then altered some more and becomes the threat it is.