Understanding Windows Firewall

Windows Firewall, previously known as Internet Connection Firewall or ICF, is a protective boundary that monitors and restricts information that travels between your computer and a network or the Internet. This provides a line of defense against someone who might try to access your computer from outside the Windows Firewall without your permission.

If you're running Windows XP Service Pack 2 (SP2), Windows Firewall is turned on by default. However, some computer manufacturers and network administrators might turn it off.

To open Windows Firewall

Click Start and then click Control Panel.
In the control panel, click Windows Security Center.
Click Windows Firewall.

Note: You do not have to use Windows Firewall?you can install and run any firewall that you choose. Evaluate the features of other firewalls and then decide which firewall best meets your needs. If you choose to install and run another firewall, turn off Windows Firewall.

How Windows Firewall Works

When someone on the Internet or on a network tries to connect to your computer, we call that attempt an "unsolicited request." When your computer gets an unsolicited request, Windows Firewall blocks the connection. If you run a program such as an instant messaging program or a multiplayer network game that needs to receive information from the Internet or a network, the firewall asks if you want to block or unblock (allow) the connection. You should see a window like the one below.

If you choose to unblock the connection, Windows Firewall creates an exception so that the firewall won't bother you when that program needs to receive information in the future.

Although you can turn off Windows Firewall for specific Internet and network connections, doing this increases the risk to your computer's security.

What Windows Firewall Does and Does Not Do

It does

Help block computer viruses and worms from reaching your computer.
Ask for your permission to block or unblock certain connection requests.
Create a record (a security log), if you want one, that records successful and unsuccessful attempts to connect to your computer. This can be useful as a troubleshooting tool.

It does not

Detect or disable computer viruses and worms if they are already on your computer. For that reason, you should also install antivirus software and keep it updated to help prevent viruses, worms, and other security threats from damaging your computer or using your computer to spread viruses to others.
Stop you from opening e-mail with dangerous attachments. Don't open e-mail attachments from senders that you don't know. Even if you know and trust the source of the e-mail you should still be cautious. If someone you know sends you an e-mail attachment, look at the subject line carefully before opening it. If the subject line is gibberish or does not make any sense to you, check with the sender before opening it.
Block spam or unsolicited e-mail from appearing in your inbox. However, some e-mail programs can help you do this. Check the documentation for your e-mail program.