Sounds obviously like spam to me. When searching you can filter out certain file extensions. To get a good idea of spam to be aware of & careful of, see Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see). (Examples shown were whilst using LimeWire, but same principle applies.)

The gnutella network is not the best place to seek program files. But yes, dmg or zip files for mac.