The built-in firewall in XP is enabled after installing SP2. The firewall will automatically block incoming traffic only. You may need to allow access of your programs by enabling them in the XP firewall.

Whenever a program attempts to access your computer, you will be prompted to instruct XP Firewall to allow this program or not:

Click Unblock this program to allow access. You should allow access if you know what the program is:

Otherwise, you should chose to Keep blocking the program or you can direct Firewall to Keep blocking this program, but ask again.

To reach this page quickly in the future, use the keyword unblock.

Send reports of security incidents, attacks, or questions to security@columbia.edu