Microsoft KB Archive/104712

FIX: Numerous Invalid Logins Cause SQL Server to Hang

PSS ID Number: Q104712 Article last modified on 10-31-1994

4.20

WINDOWS

BUG# NT: 478 (4.2)

= SYMPTOMS =

If a user repeatedly tries to log into SQL Server with an invalid login id or password, SQL Server may eventually hang. This may also hang existing connections, and any attempts to make a new connection will hang.

In addition, the following will also hang the SQL server:

  Stop SQL Server using either the SQL Service Manager (stoplight applet)   Issuing the command: net stop sqlserver 

= CAUSE =

SQL Server incorrectly handles the cleanup of invalid logins, such that after numerous (generally over 100) invalid login attempts any existing or new connections will hang.

= STATUS =

Microsoft has confirmed this to be a problem in SQL Server version 4.2 for Windows NT. This problem was corrected in SQL Server version 4.2P33. For more information, contact your primary support provider.

= MORE INFORMATION =

To see which user is trying to login to SQL Server with the invalid login id or password, you can audit the failed logins by doing the following:


 * 1) Start the SQL Server Setup program by selecting the SQL Setup icon from the SQL Server for Windows NT program group.
 * 2) From the Installation Options box, choose Set Security Options.
 * 3) In the Audit Level section of security options, check the box for Failed Logins.
 * 4) After exiting SQL Setup, stop and restart SQL Server.

After restarting SQL Server, you can periodically examine the SQL Server errorlog and/or the Windows NT Application Event Log. Any time a user tries to connect to SQL Server with an invalid login id or password, a message will be written to the errorlog and/or event log indicating the username that was denied access.

Additional reference words: 4.20 KBCategory: kbother KBSubcategory: SSrvWinNT

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Copyright Microsoft Corporation 1994.