I agree that you have a problem if you are getting viruses when using the DMZ. Make sure File and Print Sharing are turned off (Or at least you have a password on all your shares) and patch your PC. If you don't want them to be able to talk to your computer period, try blackholing their IP address... It is VERY simple to do. Just create a static route for them on either your computer or on the Cable DSL router, to an IP address that no computer occupies on a local subnet (For instance, put a route for his IP address to 192.168.10.254, when no computer is on 254 so the connection times out). If they are using TCP to establish a connection, you won't have any more problems with them :-D, and UDP will only work one way. (You will get stuff from him, but it won't go back to him)