Spoiling the network with fake files is tactic used by record and movie companies, to deter file sharers. The solution is the hash. A hash is a number that uniquely identifies a file whatever the file’s name.

Limewire has hashing to help prevent this.

Also check if you've got several choices, check for specifies hashs.

Make sure the times are similar or match.
Make the download size are simliar.
Do not download from well-known anti-p2p IP addresses.
Make its popular titled (no misspellings, unnecessary blanks or weird characters).
If it doesn't play, its probably fake.
Do not continue to download if firewall suddenly picks up a lot of connections for the riaa or its friends (RIPE, APNC)