FIX: Numerous Invalid Logins Cause SQL Server to Hang
  
PSS ID Number: Q104712
Article last modified on 10-31-1994
 
4.20
 
WINDOWS
 

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The information in this article applies to:
 
  - Microsoft SQL Server version 4.2
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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.
