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 SQL Server Security ModesAlexander Chigrik There are two security modes (authentication modes) in SQL Server 7.0/2000: The security mode is selected during SQL Server installation and can be modified at any time. For example, to change the SQL Server 2000 security modes, you can do the following: Click Start, Programs, Microsoft SQL Server and click SQL Enterprise Manager to run SQL Enterprise Manager from the Microsoft SQL Server program group. Select the server you want to work with, then from the Tools menu select SQL Server Configuration Properties, and choose the Security page.  Set SQL Server security mode. Windows NT AuthenticationWhen it is used, then Windows NT is responsible for managing user connections through its Access Control List (ACL). So, the advantage of using Windows NT Authentication is single-password access to all resources on a Windows NT domain, and password aging, and encryption across the network. Windows NT security also provides auditing, minimum password length, and account lockout after multiple invalid login requests.If Windows NT Authentication Mode is used, and a user attempts to connect to SQL Server providing nonblank login name, then the login will be ignored. This security mode is used by default, but Windows NT Authentication is not available, when SQL Server is running on Windows 9x. Mixed ModeMixed Security allows users to connect using Windows NT Authentication or using SQL Server Authentication.Mainly, SQL Server Authentication is provided for backward compatibility, but is also required when SQL Server is running on Windows 9x because Windows NT Authentication Mode is not supported on Windows 9x. When SQL Server Authentication is used, SQL Server manages its own login validation process for all connections, i.e. SQL Server is wholly responsible for authenticating a user and for enforcing password and login restrictions. You should choose Mixed Security Mode, when SQL Server running on Windows 9x, or for connections over the internet and clients other than Windows NT clients. In this case, when a user connects to a SQL Server, then SQL Server checks is it a trusted connection or not (checks is the login name matches the user's network username, or if the login name is null). If it is a trusted connection, then SQL Server uses Windows NT Authentication, if it is not a trusted connection then SQL Server uses SQL Server Authentication (i.e. tried to find the same SQL Server login name and password, as user has passed). |