Your machine will not be affected by any Windows virus and ZERO have been
successfully written to exploit Mac OS X. ZERO!
If you have lots of P/C friends or your job requires you to have some
kind of anti-virus protection, then you can prevent a virus from passing through your machine to theirs by installing something like ClamXav. (freeware)
I'm still using the older 7.2 Version of McAfee Virex and have never once found a virus in 7 years. Unfortunately Virex 7.5 is a bad CPU hog and that's why Apple does not recommend Virex 7.5
Norton's is absolutely the worst.
The most important thing you can do to protect your machine is to avoid
questionable downloads from unknown sources, incuding most P2P networks.
There IS a proof of concept "sudo" trojan that can piggyback onto another
file, then launch when the user enters their administrator password to install a program.
The risk of this can be greatly reduced by setting up a secondary SuperUser
account for all your normal daily functions, but preventing any software installs. All software installations should be limited to your primary administrative account.
It's not necessary for you to buy anti-virus software to protect your machine, but it can't hurt to have a program installed to catch something someone else sends you from passing on to someone else.
I never accept or open multiple address forwarded e-mails and politely tell
the sender that they will not be accepted.
I hope this answers your question.
