Microsoft might have released security updates that mitigate virus threats since the release of the operating system files being installed. If the new server is connected to the network and a firewall is not enabled, the server might be infected with a virus before the security updates can be downloaded and installed. Post-Setup Security Updates uses Windows Firewall to mitigate this risk.

Post-Setup Security Updates is designed to protect the server from infection between the time the server is first started and time that the most recent security updates from Windows Update are applied. To protect the server, Windows Firewall is enabled during a new installation of any version of Windows Server 2003 that includes a service pack. If Windows Firewall is enabled and the administrator did not explicitly enable it using an unattended-setup script or Group Policy, Post-Setup Security Updates opens the first time an administrator logs on. Inbound connections to the server are blocked until the administrator has clicked the Finish button in the Post-Setup Security Updates dialog box. If the administrator set exceptions to the firewall through Group Policy or by enabling Remote Desktop during installation, inbound connections assigned to these exceptions remain open.

Post-Setup Security Updates applies to Windows server administrators who are performing a full installation of Windows Server 2003 that includes a service pack (such as a slip-stream version of Windows Server 2003 with SP1). This feature does not apply if either of the following cases:

Post-Setup Security Updates does not apply if the administrator is updating an existing Windows Server 2003 operating system by adding a service pack or if the administrator is upgrading an existing Windows 2000 Server operating system to Windows Server 2003 with SP1.

Post-Setup Security Updates does not cause any applications to work differently. Manage Your Server is not displayed until Post-Setup Security Updates closes. However, Manage Your Server is available from the Start menu. Under the circumstances we’ve described above, Windows Firewall can now be enabled automatically until Post-Setup Security Updates is finished.