1. Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see), get to recognise them. Select those that are obviously spam junk, then press Junk button so it signifies them as Junk. Eventually the Junk filter learns they are junk (it's not a perfect tool though & sometimes gets it wrong.) Show junk results at bottom of search results.

2. Add the Hostiles List, though if you're using the Alpha version, I think it's built in.