Restricting Access to Ports
Internet architects originally envisioned assigning each new protocol or service its own port number so that it could be easily found and used on any computer. They succeeded, but their plan worked too well. Friendly computers in a local network can find the services easily, but so can any computer connected to the Internet, whether it's being used by friend or foe. Paring down the list of ports that can be accessed in your network is an essential security measure.
Windows includes three different mechanisms that can help secure a system by filtering traffic:
Windows Firewall (available only in Windows XP) is an easy-to-configure tool that you can use to block all incoming traffic except for responses to communications ...
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