UDP port 13404

I'm getting a large number of hits at my firewall on UDP port 13404,
coming from a variety of different IP addresses (searching whois on a
few random samples, they appear to be spread around the world).

Obviously these are blocked by my firewall, but I'm curious if anyone
knows what might be using this port? My guess is that it is a worm of
some sort, but the other possibility is that it is some sort of file
sharing or P2P network.

mvh.,

David