JSI Tip 7109. How do I disable DCOM support in RPC over HTTP on Windows Server 2003?

Microsoft Knowledge Base Article 826382 contains the following summary:

Windows Server 2003 provides support for implementing the remote procedure call (RPC) protocol over HTTP, known as "RPC over HTTP." By default, RPC over HTTP support is not installed when you install Windows Server 2003, but you can enable it by using Add/Remove Programs.

To determine if you have support for RPC over HTTP enabled on servers running Windows Server 2003, follow these steps:

If the RPC over HTTP Proxy check box is selected, RPC over HTTP support is enabled on the server.

DCOM is a protocol that can be used on top of the RPC protocol by client / server applications. By default, a server running Windows Server that is configured to support RPC over HTTP will also accept DCOM requests using this protocol. These DCOM requests are then sent to a local port on the server implementing RPC over HTTP (TCP port 593).
Security best practices recommend disabling or removing all nonessential components and services.

If DCOM support is not required on your RPC over HTTP servers, you can remove DCOM support by modifying the registry. To use RPC over HTTP to remove DCOM support, follow these steps:WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

When you remove entries for port 593, you prevent DCOM from being used through the RPC over HTTP protocol, but RPC programs (like the Outlook 2003 client) are permitted to connect to the RPC server (Exchange 2003 Server) through RPC over HTTP.

When you use RPC over HTTP to remove DCOM support, you can help mitigate the vulnerabilities that are addressed in security bulletin MS03-026 for servers that expose RPC services over HTTP ports 80,443.