Hmm, well you might be right that it does not use the entire open source database, but if you compare File::Scan's signature.txt and the virus.db of clamscan, they are almost the same, except for some formatting. As a matter of fact, when I first played with File::Scan, I imported the open source virus database into it's signature's.txt file. With such a huge signature file, File::Scan was so slow it was unusable, where clamav remained quite fast. Virus scanning is still best done with c.