Apple is fighting what security experts say may be the most pernicious types of computer virus to ever target its line of Mac computers.

The company has issued a security advisory warning to customers about a recent scam that infects Macs with malicious software that wrongly tells them their computer is infected with a virus. The ultimate goal is to get credit card numbers and other valuable personal information.

It is one of the first major campaigns that cyber crooks have launched against Mac users. To date, criminals have focused on writing malicious software for machines running Microsoft's Windows operating system, which inhabits more than nine of every 10 personal computers.

But as Macs have grown in number, they have become more attractive targets.