Most effective Windows viruses activate themselves as soon as they are downloaded onto a computer using an auto-execute flaw in Windows. Then they just do their destructive thing.
It is difficult to create viruses for Macs that will spread effectively because unlike Windows based computers, the Mac user has to actually activate the virus.
There is a new Mac virus spreading around that uses an old trick fairly effectively. Since Mac users have to activate the virus themselves (and who would knowingly do that?) the iServices.B virus has been hidden in applications downloadable via BitTorrent.
***Let me make it clear. If you buy legal versions of these software packages, you will not have any problems!***
The virus is only hidden in some illegally downloadable versions of the iWorks 2009 and Adobe Photoshop CS4.
My recommendations are to refrain from downloading these applications, or at the very least… get a functioning copy from someone else who has installed it on their own machine. Then you will know if it is legit.
Just because the virus has only been found in illegal versions of iWorks 2009 and Adobe Photoshop CS4 does not mean that it will not turn up in other applications.
Be mindful of what you download and install on your computer.
Always practice safe computing.