You may not be able to connect to an instance of SQL Server by using an anonymous login

When you add the NT AUTHORITY\ANONYMOUS LOGON login to your instance of Microsoft SQL Server 2000 or Microsoft SQL Server 2005 so that the instance of SQL Server accepts anonymous logins through Microsoft Windows Integrated security and then you try to connect to the instance of SQL Server as an anonymous user, the connection attempt may not be successful and you may receive the following error message:Additionally, the following event is logged in the system event log:This problem occurs when all the following conditions are true:

• The instance of SQL Server is installed on a computer that is running Microsoft Windows Server 2003.
• The computer that is running the instance of SQL Server is a member server in a domain.
• The HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\TurnOffAnonymousBlock registry value is either missing or is not set to 1.
• The Network Access: Allow anonymous SID/Name translation security option on the computer that is running the instance of SQL Server is not enabled.

When you try to connect to the instance of SQL Server as an anonymous user, the anonymous connection tries to open the LSA Policy handle on the computer that is running the instance of SQL Server. By default, a Windows Server 2003 member server denies an anonymous connection attempt that tries to open an LSA Policy handle if the TurnOffAnonymousBlock registry value is not set to 1. Therefore, your anonymous connection is not successful. Additionally, after SQL Server receives the anonymous connection request, SQL Server calls the LookupAccountSid Windows API function to obtain the account name. Because the function is called in the context of the anonymous connection, the function call also fails if the Network Access: Allow anonymous SID/Name translation security option is not enabled.

Warning This workaround may make your computer or your network more vulnerable to attack by malicious users or by malicious software such as viruses. We do not recommend this workaround but are providing this information so that you can implement this workaround at your own discretion. Use this workaround at your own risk.

To work around this problem, follow these steps on the computer that is running Windows Server 2003 to allow anonymous connections to SQL Server 2000 or to SQL Server 2005:

1. Enable the Network Access: Allow anonymous SID/Name translation security option in Local Security Policy. To do this, follow these steps:
   1. Click Start, and then click Control Panel.
   2. Double-click Administrative Tools, and then double-click Local Security Policy.
   3. In the left pane, expand Local Policies, and then click Security Options.
   4. In the right pane, under the Policy column, locate and then double-click Network Access: Allow anonymous SID/Name translation.
   5. In the Network Access: Allow anonymous SID/Name translation dialog box, click the Enabled option, and then click OK.
   6. Close the Local Security Settings window.
   7. Close the Administrative Tools window.
2. Set the TurnOffAnonymousBlock DWORD registry value to 1. To do this, follow these steps.
   
   Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
   322756  (http://support.microsoft.com/kb/322756/ ) How to back up and restore the registry in Windows
   1. Click Start, click Run, type regedit, and then click OK.
   2. In Registry Editor, locate and then click the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa registry key.
   3. In the right pane, locate and then double-click the TurnOffAnonymousBlock DWORD registry value.
      
      Note If the TurnOffAnonymousBlock DWORD registry value does not exist, you must create the registry value.
   4. In the Edit DWORD Value dialog box, type 1 in the Value data box, and then click OK.
   5. Close Registry Editor, and the restart the computer. A restart is required for the registry changes to take effect.

Note By default, the Network Access: Allow anonymous SID/Name translation security option is enabled on the computers that act as domain controllers. However, the security option is disabled on workstations and member servers. The domain controllers do not require the TurnOffAnonymousBlock registry key to control the anonymous connection attempts. Therefore, if your instance of SQL Server is installed on a domain controller that is running Windows Server 2003, the anonymous connection attempts to the instance of SQL Server do not fail.

On a computer that is running Windows Server 2003, security checks that are performed on the anonymous connections that try to access the computer are more stringent. If you create a Microsoft ASP.NET page that uses Windows authentication and impersonation on a Web server that is running Microsoft Internet Information Services (IIS) 6.0 but you cannot delegate the user accounts, any attempts to connect to a remote instance of SQL Server from the ASP.NET page are in the security context of the NT AUTHORITY\ANONYMOUS LOGON login. You can configure your instance of SQL Server to accept the anonymous connections through Windows Integrated security by adding the NT AUTHORITY\ANONYMOUS LOGON login as a SQL Server user and by granting the required permissions to the user. When you add the NT AUTHORITY\ANONYMOUS LOGON login to your instance of SQL Server, anonymous connections can access SQL Server data without providing any logon credentials.

Important We do not recommend allowing anonymous access to SQL Server. All permissions that are granted to the NT AUTHORITY\ANONYMOUS LOGON login can be used by any user who can connect to the computer that is running SQL Server. If you must allow anonymous access to your instance of SQL Server, we recommend that only read permissions are granted to the NT AUTHORITY\ANONYMOUS LOGON login to view the SQL Server data that you want to be publicly viewable. Additionally, we recommend that only Execute permissions are granted to the SQL Server stored procedures that perform limited operations.

Instead of allowing the anonymous connections to your instance of SQL Server, you can grant the required access to a specific SQL Server account and pass the logon credentials for the SQL Server account in the connection string in the ASP.NET page. Using SQL Server authentication avoids the anonymous connection attempts to the instance of SQL Server and is more secure.

If the Network Access: Allow anonymous SID/Name translation security option is enabled on the computer that is running Windows Server 2003, all the users who can make a network connection to the computer can look up the account names for any known security identifications (SID), such as the Administrator account. A malicious attacker may use this information to connect to the server by using a method such as password guessing or to lock out the accounts with failed login attempts.

If you set the value of the TurnOffAnonymousBlock registry value to 1, the anonymous connections can open a handle to the policy for the Local Security Authority. For more information about the LSA Policy, visit the following MSDN Web sites:

For additional information about troubleshooting the connectivity issues in SQL Server 2000, click the following article number to view the article in the Microsoft Knowledge Base: For additional information, click the following article number to view the article in the Microsoft Knowledge Base: