Microsoft has updated their "Deploying Windows Firewall Settings for Microsoft Windows XP with Service Pack 2" white paper

Windows XP Service Pack 2 (SP2), currently a Release Candidate in Beta testing, includes significant enhancements to the Windows Firewall component, previously known as the Internet Connection Firewall (ICF). Windows Firewall is a stateful host-based firewall that discards unsolicited incoming traffic, providing a level of protection for computers against malicious users or programs. To provide better protection for computers connected to any kind of network (such as the Internet, a home network, or an organization network), Windows XP SP2 enables Windows Firewall on all network connections by default. This new behavior can impair some types of communications. This article describes how to deploy the appropriate configuration settings for Windows Firewall on an organization network so that it is enabled and providing protection, and so that communications are not impaired.

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