Heaps of infected files are shared on the network. Some are shared to sabotage p2p & some are shared because people aren't aware that the file they're sharing is infected. Check out the links below for more info & always scan a downloaded file with a good, updated AV program, before you open it


Virus thread: Typical virus spam file sizes - Make a note of them (click on blue link to see)

* WARNING: Viruses on network you should be aware of ! *


And some links with info about bad files being deliberately shared in this thread: Fake files showing up in search results