On NT Server right click on Network neighorhood, click on the protocols Tab, double click on TCP/IP, on the bottom right corner click on Advanced... on the bottom of Advanced IP Addressing box click on Enable Security, then click on Configure, in the TCP/IP Security you can permit TCP or UDP ports, that is if you know which ports you want just don't enter the ports you want blocked, that should work. If you don't want to go this route then install MS Proxy Server 2.0 this would be the best way to go. Good luck.