I've gotten about 15 virus loaded messages today and I think I figured out a way to filter them directly to the trash without harming my normal mail. The messages all look identical to me in Eudora, they're completely blank except for a multipart inline attachment of some sort. You can't contact the infected person because the virus, as it propigates, rewrites the From line to be the user's first name and last name preceded by an underscore. That's how I found a way to filter it out, by searching for that initial "_" character.
Create a new filter, and look for "