These files are autogenerated along with whatever you search for. It's an anti-p2p project designed to stop people's enthusiasm for using p2p programs. Google Overpeer to get an idea of sponsored groups who are set up to do this.

Avoid files less than 1 MB or 2 MB (2,000 KB) for help stay away from these & not be confused by them showing up in results. See Arrange search results by size (click on link) to help keep those results at the bottom of the search results window so you know what they are. You can keep using the Junk filter to try to filter them out. The Junk filter is a dynamic learning filter. But viruses are the hardest to filter out. It takes time & patience & perserverence. The other spam types like the iPod advert, etc. are very easy & fast to filter out.