This article is from the Viruses and the Mac FAQ, by David Harley D.Harley@icrf.icnet.uk with numerous contributions by others.
Any Mac running any sort of DOS or Windows emulation such as
Virtual PC, SoftPC, SoftWindows, RealPC, or a DOS compatibility
card is a potential target for any PC virus, including Boot Sector
Infectors/Multipartites; (effects will vary). It is highly
recommended that anyone with such a system should run a reputable,
up-to-date PC antivirus program under emulation, as well as a good
Mac antivirus program. [Dr. Solomon's for the Mac detected PC boot
sector infectors as well as Mac viruses, but didn't detect PC file
viruses (apart from macro viruses), and so was not sufficient
protection for a Mac with DOS emulation.]
Recommendations for defending PC systems or PC emulation on Macs
are slightly out-of-scope for this FAQ. In fact, I don't know of
any formal testing for PC antivirus software in the context of PC
emulation on Macs. I've done some informal testing (referred to in
another paper), but am not prepared to make vendor-specific
recommendations on the basis of such testing. F-Prot, AVP, and Dr
Solomon's are particularly well-regarded PC antivirus packages, of
which some components on some platforms are available as freeware
or for evaluation, but their efficacy in the context of PC
emulation is not well tested or documented.
To find a commercial or shareware package relevant to PCs, check
through the independent comparative reviews sites:
University of Hamburg Virus Test Center
University of Tampere Virus Research Unit
+ About.com has an aggregation of PC anti-virus reviews links.
Robert Michael Slade's lists may also be helpful.