adware/spyware removal for Macs?

Are there any free spyware removal programs that are mac compatible?

edit: I'm asking this because my friend that has a iBook is getting popups whenever she uses firefox. I'm not sure if this is a virus or just spyware/adware. Any help on some free programs would be helpful. Thanks!

So there's nothing to remove the pests on my friend's iBook? =(

c'mon dude... google

http://www.google.com/search?client=opera&rls=en&q=anti+spyware+mac&sourceid=opera&ie=utf-8&oe=utf-8