Filters such as keyword filters do have their limits. I don't know which client p2p app you're using but for LW (which is the one I know), you can add words such as .wmv & .jpg to block those adverts. But, if you're searching for those types of files then you need to remove those filters during that time. After a while you recognise the size of these spam files, & that they originate from T1 sources & are generally in the greatest number. I think that says it all really. Apparently LW for example is thinking about introducing a size filter (I've been pushing them to do it for well over 6 months) to help with this cause plus help people get more accurate search results. There's other p2p apps out there that use size filters.
eg:
http://www.gnutellaforums.com/showth...threadid=33325