After installation of Windows NT 4.0 Service Pack 3 or the Windows NT 3.51 hotfix, administrators who want to require only authenticated users to list account names, and exclude anonymous connections from doing so, need to make the following change to the registry: 

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk. 



1.Run Registry Editor (Regedt32.exe). 

2.Go to the following key in the registry: 





      HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\LSA





3.On the Edit menu, click Add Value and use the following entry: 





      Value Name: RestrictAnonymous
      Data Type:  REG_DWORD

      Value:      1






4.Exit the Registry Editor and restart the computer for the change to take effect. 



The purpose of the registry value is to configure local system policy for whether authentication is required to perform common enumeration functions. Requiring authentication to obtain the account name list is an optional feature. When the RestrictAnonymous value is set to 1, anonymous connections from the Graphical User Interface tools for security management will receive an access denied error when attempting to get the list of account names. When the RestrictAnonymous value is set to 0, or the value is not defined, anonymous connections will be able to list account names and enumerate share names. It should be noted that even with the value of RestrictAnonymous set to 1, although the user interface tools with the system will not list account names, there are Win32 programming interfaces to support individual name lookup that do not restrict anonymous connections. 



Windows NT networks using a multiple domain model can restrict anonymous connections without loss of functionality. The initial steps in planning to disable anonymous connections is for administrators in resource domains to add members of trusted account domains to specific local groups as needed before changing the value for the LSA RestrictAnonymous registry entry. Users logged on using accounts from trusted account domains will continue to use authenticated connections to obtain list of account names to manage security access control. 





Restricting Anonymous List of Share Names

The Server service that provides remote file access to share resources will also use the LSA registry value, RestrictAnonymous, to control whether anonymous connections can obtain a list of share names. Therefore, administrators can set the value of a single registry configuration entry to define how the system responds to enumeration requests by anonymous logons. 





Restricting Anonymous Remote Registry Access

Installation of Windows NT 4.0 Service Pack 3 or the Windows NT 3.51 hotfix removes the ability for anonymous users to connect to the registry remotely. Anonymous users cannot connect to the registry and cannot read or write any registry data. As a reminder, Windows NT 4.0 restricts remote access to the registry by domain users using the access control list on the registry key: 



   HKEY_LOCAL_MACHINE\SYSTEM\Control\CurrentControlSet
   \SecurePipeServers\winreg




The ACL on this key identifies the authenticated users allowed to remotely connect to the registry. Windows NT 4.0 Server, by default, only allows Administrators remote registry access. The winreg\AllowedPaths subkey identifies specific portions of the registry that authenticated users who are not explicitly granted access by the winreg ACL can use for printer access and other system operations. The winreg key may be defined on Windows NT 4.0 Workstations to restrict remote registry access to those systems. For more information on the winreg key, please see the following article in the Microsoft Knowledge Base: