A. The Windows Firewall monitors all network traffic on the connections for which it is enabled. For example, the firewall can monitor all traffic on your dial-up connection to the Internet. The firewall keeps track of all communications that have originated from your computer, and it prevents unsolicited traffic from reaching your computer. If necessary, the firewall dynamically opens ports and allows your computer to receive traffic that you have specifically requested, such as a Web page for which you have clicked the address.

A "port" is a networking term that identifies the point at which a type of network traffic reaches your computer. The exact ports that you open depend on the type of traffic you want to send and receive.

If you have not requested the incoming traffic, Internet Connection Firewall helps block it before it can reach your computer. For special uses, such as networking, hosting online games, or hosting your own Web server, you can select ports that you want to leave open. This allows others to make connections to your computer, but it can also reduce security.

Internet Connection Firewall is part of Windows XP Home Edition and Windows XP Professional.

To learn more read Use the Internet Connection Firewall and How to Open Ports in the Windows XP Internet Connection Firewall.