Wil with a look at all the antivirus apps on the Mac App Store:
Yes, Macs can be infected with malware and there are enough antivirus apps out there to tell you malware is a problem somewhere on someone’s Mac. But where?
I’ve used a few antivirus and malware detection apps and never found anything of consequence.
For Macs that I know have been infected with some variant of malware, it’s usually because the Mac user visited a website or downloaded an infected application.