answer:Anything is possible, but the nature of UNIX and UNIX-like operating systems would keep anything from becoming wide-spread. With such a small market share, it is like throwing a dart at a wall of 10,000 balloons and hitting the one that is a Mac. Proof of concept viruses exist, but the trick is to get someone to execute an malicious bit of code without the user getting a prompt for the admin password. Long story short, I am not worried about it. If you are, try CLAM - X , a free antivirus for the Mac. I wouldn't waste my money on Norton.