The Restrictions for Unauthenticated RPC clients machine setting should be configured correctly. If you enable this setting, it directs the RPC Runtime on an RPC server to restrict unauthenticated RPC clients connecting to RPC servers running on a machine. A client will be considered an authenticated client if it uses a named pipe to communicate with the server or if it uses RPC Security. RPC Interfaces that have specifically asked to be accessible by unauthenticated clients may be exempt from this restriction, depending on the selected value for this policy. If you disable this setting or do not configure it, the value of Authenticated will be used for Windows XP and the value of None will be used for Server SKUs that support this policy setting. Fix: (1) GPO: Computer Configuration\Administrative Templates\System\Remote Procedure Call\Restrictions for Unauthenticated RPC clients (2) KEY: HKLM\SOFTWARE\Policies\Microsoft\Windows NT\Rpc\RestrictRemoteClients