ClamAV is used quite a bit by email services, who make a large contribution to its virus signature database. Is the average Windows PC user or workstation user more apt to encounter viruses and other malware on Web sites, chat rooms, and instant messenger services than email viruses? This type of malware targets system exploits and is composed of several pieces of malware in a "package." If it is different, then ClamWin needs a separate database that contains the signatures for these types of malware. This could be why ClamAV (and ClamWin by extension) doesn't compare well on some tests of antivirus software that you hear about. The Univ. of Magdeburg recently did another one, and I understand that ClamAV found close to 50% of the test viruses, compared to better than 90% for the big names in antivirus software.

Regards,