Allow NTLM to fall back to NULL session when used with LocalSystem. The default is TRUE up to Windows Vista and FALSE in Windows 7. Fix: (1) GPO: Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options!Allow NTLM to fall back to NULL session when used with LocalSystem. (2) REG: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Lsa\MSV1_0!allownullsessionfallback