NET 3.5 creates an ACL (Access Control List) for the namespace "http://+:8731/Design_Time_Addresses" during the installation of Visual Studio so users without administrator privilege are able to develop WCF services. The ACL is set to (UI), which includes all interactive users logged on to the machine. Administrators can add or remove users from this ACL, or open additional ports.
This ACL enables WCF or WF templates to send and receive data in their default configuration. It also enables users to use the WCF Service Auto Host (wcfSvcHost.exe) without granting them administrator privileges.
You can modify access using the netsh.exe tool in Windows Vista under the elevated administrator account. The following is an example of using netsh.exe.
netsh http add urlacl url=http://+:9002/MyService user=\
TIP: If you are developing as Administrator and also you have disabled Windows Vista UAC (User Account Control), then you shouldn't have to deal with this matter. You could choose any URI you want. But, you'd better do a good testing with no Administrators users before deploying your WCF Service, or you'll be facing this security control when you don't have time to deal with it (deployment phase, production environment, etc.).