Hackers write for maximum exposure...there are 10000x more windoze boxes out there, so that's what the hackers write them for. Believe me, you can write a virus/trojan/malware program for mac or linux just as easily ( relatively speaking ), but since there are sooo many more UNPROTECTED windoze boxes out there, thats what gets the lion share.
BTW, I don't understand why so many people use McAffe..it used to be good..back in the day, but now its such a memory/resource hog, its turned into 'bloatware' ( like Nero IMHO ). Probably because its the cheapest lol ... Panda & Kapersky rock, but Panda had a major finger-pointing issue with SpySweeper, so I use Kapersky.