OSX isn't virus proof, but times have changed. Most infections these days are written by criminals who are trying to grab credit cards, set up file shares, or bots for spamming or launching denial of service attacks. The days of some disgruntled Eastern European kiddie writing something to delete your hard disk and nothing else are mostly gone.

However it's accomplished, Mac users don't worry about viruses or spyware.

Whistling through the graveyard maybe, but there it is.