Track Account Lockouts Using the Checked Netlogon.dll

by Wayne Maples [Published on 20 April 2004 / Last Updated on 20 April 2004]

Large numbers of failed logins due to bad passwords is a red flag for intrustion detection. If you need to generate more detailed data to track bad password attempts to Windows NT domains, install the checked build of Netlogon.dll on the PDC. This will create %systemroot%\debug\Netlogon.log which will capture more information on the bad password attempts. You will need to obtain the checked version of Netlogon.dll from Microsoft support or its on the Microsoft DDK. To start generating the log:
  • stop netlogon service on PDC
  • rename original netlogon.dll to netlogon.dll.original
  • copy checked version of netlogon.dll to system32 directory
  • set HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Netlogon\Parameters\DBFlag to 0x20000004.
  • start netlogon service on PDC

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