Part of my role at Sun is responsibility for the certification of antivirus software with
Sun StorageTek 5000 NAS Appliances
Certification is the final step of the process required to enable a NAS Appliance to work with an antivirus software product. Prior to certification the NAS Engineering team has to work with the antivirus ISV to ensure that our products work correctly together as all antivirus products work slightly differently.
The way that NAS appliances scan files for viruses is a surprise to many people and I recently wrote an article for the Sun Developers Network on this topic. If you are interested the article, it is here: Protecting CIFS Clients From Viruses Using Sun StorageTek NAS OS. The scanning model described is common to NetApp and EMC NAS appliances..though we are one of the first to standardize on ICAP (see the article if you are getting curious).
The title of the article is very specific in that it references CIFS. As is normal with all the other NAS appliances I have looked at, files that are accessed over NFS are not candidates to be virus scanned (unless they are accessed over CIFS as well as NFS).
I have written a much longer White Paper on this topic that I hope to get posted on www.sun.com sometime soon.