Cannot connect to SQL database on Windows NT Server computer with IIS

On a Windows NT Server computer running Internet Information Server (IIS) version 3.0, 4.0, or 5.0, the following ODBC error message appears when you try to verify a connection to a remote SQL database:

Microsoft SQL Server Integrated Security requires NTLM authentication in order to map user accounts to SQL Server accounts.

After a Web browser is authenticated by IIS, an authenticated connection to the SQL Server is not possible. IIS is using the IUSR account when it attempts to connect to SQL Server. When using the IUSR account to connect to the SQL Server, NTLM authentication is used.

Essentially, IIS does not have the necessary information to complete the NT authentication process.

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

To work around this issue, use one of the following methods:

Method 1: Host IIS and SQL Server on the Same Computer

By eliminating the need for IIS to create an authenticated connection to SQL Server, you can work around this issue.

To do this, you must use a data source name (DSN) that looks directly to the local computer for the SQL Server, and not to the network. This can be done by using the "(local)" setting in a System DSN.

Method 2: Use Basic Authentication Instead of NTLM in IIS

By using Basic Authentication, the password is BASE64 encoded and sent to IIS during the authentication process. With the password, IIS can now complete the NTLM authentication process when connecting to SQL Server.

Note With Basic authentication, we recommend that the data be encrypted by using SSL because it is very easy to obtain credentials from a network trace.

Method 3: Map the Anonymous User Account from IIS to a SQL Server Guest Account

This method assumes that all users will have the same level of privileges to the SQL Server resources. Every user browsing to the Web will have access to the database.