Fake security software for Apple computers called MacDefender has shot to the top of Apple forum complaints.
Like the much more common PC forms of so-called "scareware", MacDefender appears to scan computers, reports bogus issues and then offers to fix them for a fee.
The software also links to pornographic websites to trick victims into thinking their computer is infected and pressuring them into parting with cash.
Security experts say that, although such attacks are much lower than similar attacks aimed at users of the Microsoft Windows operating system, they do exist and cannot be ignored.
Although the attacks targets both Mac and Windows users, it may more easily trick Mac users as it sometimes poses as a legitimate security program called MacDefender, says Graham Cluley, senior technology consultant at Sophos.