Common Causes for Account Lockouts

from Microsoft Technet


Programs:
Many programs cache credentials or keep active threads that retain the credentials after a user changes their password.

Service accounts:
Service account passwords are cached by the service control manager on member computers that use the account as well as domain controllers. If you reset the password for a service account and you do not reset the password in the service control manager, account lockouts for the service account occur. This is because the computers that use this account typically retry logon authentication by using the previous password. To determine whether this is occurring, look for a pattern in the Netlogon log files and in the event log files on member computers. You can then configure the security control manager to use the new password and avoid future account lockouts.

Bad Password Threshold is set too low:
This is one of the most common misconfiguration issues. Many companies set the Bad Password Threshold registry value to a value lower than the default value of 10. If you set this value too low, false lockouts occur when programs automatically retry invalid passwords. Microsoft recommends that you leave this value at its default value of 10. For more information, see "Choosing Account Lockout Settings for Your Deployment" in this document.

User logging on to multiple computers:
A user may log onto multiple computers at one time. Programs that are running on those computers may access network resources with the user credentials of that user who is currently logged on. If the user changes their password on one of the computers, programs that are running on the other computers may continue to use the original password. Because those programs authenticate when they request access to network resources, the old password continues to be used and the users account becomes locked out. To ensure that this behavior does not occur, users should log off of all computers, change the password from a single location, and then log off and back on.
Note:
Computers running Windows XP or a member of the Windows Server 2003 family automatically detect when the users password has changed and prompt the user to lock and unlock the computer to obtain the current password. No logon and logoff is required for users using these computers.

• Stored user names and passwords retain redundant credentials:
If any of the saved credentials are the same as the logon credential, you should delete those credentials. The credentials are redundant because Windows tries the logon credentials when explicit credentials are not found. To delete logon credentials, use the Stored User Names and Passwords tool. For more information about Stored User Names and Passwords, see online help in Windows XP and the Windows Server 2003 family.
Note:
Computers that are running Windows 95, Windows 98, or Windows Millennium Edition do not have a Stored User Names and Passwords file. Instead, you should delete the user's .pwl file. This file is named Username.pwl, where Username is the user's logon name. The file is stored in the Systemroot folder.

• Scheduled tasks:
Scheduled processes may be configured to using credentials that have expired.

• Persistent drive mappings:
Persistent drives may have been established with credentials that subsequently expired. If the user types explicit credentials when they try to connect to a share, the credential is not persistent unless it is explicitly saved by Stored User Names and Passwords. Every time that the user logs off the network, logs on to the network, or restarts the computer, the authentication attempt fails when Windows attempts to restore the connection because there are no stored credentials. To avoid this behavior, configure net use so that is does not make persistent connections. To do this, at a command prompt, type net use /persistent:no. Alternately, to ensure current credentials are used for persistent drives, disconnect and reconnect the persistent drive.

• Active Directory replication:
User properties must replicate between domain controllers to ensure that account lockout information is processed properly. You should verify that proper Active Directory replication is occurring.

• Disconnected Terminal Server sessions:
Disconnected Terminal Server sessions may be running a process that accesses network resources with outdated authentication information. A disconnected session can have the same effect as a user with multiple interactive logons and cause account lockout by using the outdated credentials. The only difference between a disconnected session and a user who is logged onto multiple computers is that the source of the lockout comes from a single computer that is running Terminal Services.

• Service accounts:
By default, most computer services are configured to start in the security context of the Local System account. However, you can manually configure a service to use a specific user account and password. If you configure a service to start with a specific user account and that accounts password is changed, the service logon property must be updated with the new password or that service may lock out the account.

Other Potential Issues:

  • Account Lockout for Remote Connections
  • Internet Information Services
    By default, IIS uses a token-caching mechanism that locally caches user account authentication information. If lockouts are limited to users who try to gain access to Exchange mailboxes through Outlook Web Access and IIS, you can resolve the lockout by resetting the IIS token cache.
  • MSN Messenger and Microsoft Outlook
    If a user changes their domain password through Microsoft Outlook and the computer is running MSN Messenger, the client may become locked out.

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