Apple has urged Mac owners to use anti-virus software.
In a note posted on its support site in late November, Apple said it wanted to
"encourage" people to use anti-virus to stay safe online.
The move is widely seen as a response to the growing trend among cyber
criminals of booby-trapping webpages that can catch out Mac users.
Before now Mac users have been largely free of the security problems that
plague Microsoft's Windows.
Fresh threat
The support note recommends that Mac owners install one or more of three
anti-virus products.
Advice on the site said: "Apple encourages the widespread use of multiple
antivirus utilities so that virus programmers have more than one application to
circumvent, thus making the whole virus writing process more difficult."
Apple recommended users try McAfee VirusScan, Symantec Norton Anti-Virus 11, or
Intego VirusBarrier X5.
The vast majority of malicious programs circulating online are aimed at
Microsoft's Windows, largely because the software is used by so many people.
A handful of viruses have been written that targets Mac's OSX, but most have
been demonstration versions only and few have had any significant impact on
Apple users.
One virus, known as AppleScript.THT, could take control of a Mac and grab
screenshots or keystrokes.
However, in recent months, hi-tech criminals have signalled a change in tactics
away from e-mail borne viruses. Instead, many are infiltrating popular webpages
in a bid to infect the machine of any and every visitor.
Many seek to steal valuable information such as login names, passwords or game
accounts instead of trying to install themselves on a machine.