Internet Connection Firewall

A firewall is designed to act as a protective boundary between the Internet and computers on a local network. Microsoft Windows XP includes the Internet Connection Firewall to guard your home network against external threats by making sure that any incoming information matches outgoing requests. ICF does this by maintaining a list of all communication that crosses its path, inspecting the source, destination, and content of each transfer. To prevent unsolicited traffic from the Internet, ICF then compares each message to a table of outbound messages originating from within the network. Inbound traffic is only allowed when there is a match. If there isn't a match, ICF drops the inbound traffic.

If your home network uses Internet Connection Sharing to provide Internet access to multiple computers, the Internet Connection Firewall should be enabled on the shared Internet connection. The firewall is automatically enabled when the Home Networking Wizard is run on the host computer.

Internet Connection Sharing doesn’t need to be enabled for you to use the Internet Connection Firewall. You can enable the Internet Connection Firewall on any Internet-connected computer that uses Windows XP.

To enable the Internet Connection Firewall:

1.	Click the Start button on the Windows taskbar, click Control Panel, and then click Network and Internet Connections.

2.	In Network and Internet Connections dialog box, click Network Connections.

3.	Right-click the Dial-up, LAN, or High-Speed Internet connection you want to protect, and click Properties.

4.	Click the Advanced tab, and select the Protect my computer and network by limiting or preventing access to this computer from the Internet check box.

5.	Click OK.

Note: You shouldn't use the Internet Connection Firewall in an existing network with other Windows 2000 domain controllers, DNS servers, gateways, or systems configured for static IP addresses. Some programs, such as Microsoft Outlook 2000, might behave differently once a firewall is enabled. However, Microsoft Outlook Express will not be affected.