Marcus, you are right. It is a kind of scanner.
For more info follow the next link:
http://gcachescan.jonatkins.com/ 
The question is: "do you want to be on the GNUTELLA list of webcaches?"
The answer is simple: "NO, you serve MUTE_net and not Gnutella"
What can you do: "Nothing, if you did not signup yourself then someone else did it for you. Thanks to this person your cache gets hit by all those Gnutella clients who's call will be refused by the cache".
This is the main reason that you should use a cname for your cache in stead of using your webservers IP-address.
As I said before, from the moment you stop running your cache, your webservers IP-address (should you have used that) will still be hit by thousands of P2P-clients.
If you used a cname, only DNS servers will be hit.
DNS servers can handle this kind of punishment (they are build for it and have special routines for it) but I don't think that your webserver still performs under these conditions if you used its IP-address.
