The Cult of Mac Blog writes about the rather nasty little Opener malware that’s been found for OS X:
“There’s no means for Opener to spread, and no way for it to infect a machine remotely.”
It’s worth noting that this strictly isn’t true. Opener will, according to the original Macintouch report, copy itself to any mounted volume, presumably including servers. It also turns on File Sharing and puts a copy into each user’s Public (shared) folder. Another user opening one of these copies would, if they put in their admin password, be infected themselves. So while Opener has nothing like the kind of exploit that spread Sasser, it does have a crude method of spreading.