This was a post written several years ago but principle still applies, and applies to spammers, believe it or not; Quality of Content on the Network (click on link). But the gnutella community is trying to fight against spammers in one way or another. Recognising their style & their file sizes helps greatly. Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)

For videos, Bitzi look up helps greatly. Bitzi needs much more user input. How to use Bitzi Web Lookup