The issue you're experiencing with domain account lockouts after upgrading to Windows 11 could be related to several factors, particularly concerning how Windows 11 handles credentials and security policies. Here are some considerations and troubleshooting steps based on your description:
- Account Lockout Policy: Windows 11 may be triggering account lockouts due to the way it handles cached credentials or other security features. The default account lockout threshold in a managed domain is typically set to lock accounts after a certain number of failed login attempts (e.g., 5 bad password attempts within 2 minutes). This is designed to protect against brute-force attacks.
- Cached Credentials: If the upgraded PCs are using old or cached credentials that are no longer valid, this could lead to repeated lockout attempts. It's good that you've cleared saved credentials in the Credential Manager, but ensure that no applications are trying to authenticate using outdated credentials.
- Windows Hello for Business and Credential Guard: These features could also be influencing the behavior of account logins. If any of the PCs were using Windows Hello or Credential Guard prior to the upgrade, ensure that these settings are properly configured post-upgrade.
- Event Log Analysis: Since you've noted that the lockout attempts are generated by the SYSTEM context, it may be beneficial to further analyze the security event logs for any specific applications or services that may be attempting to authenticate using the domain account. Look for patterns or specific services that might be causing the lockouts.
- Network and Security Configuration: Ensure that there are no changes in network security configurations or group policies that might affect how authentication is handled post-upgrade. Sometimes, security policies can inadvertently cause issues with account authentication.
- Known Issues and Fixes: While there may not be a specific hotfix for this issue, keeping Windows 11 updated is crucial, as Microsoft frequently releases updates that address bugs and improve security features. Check for any updates or patches that might relate to account lockout issues.
- Testing in a Controlled Environment: If possible, replicate the issue in a controlled environment to better understand the root cause. This could involve testing with different configurations or user accounts to see if the problem persists.
Given the complexity of the issue and the potential impact on your organization, it may also be beneficial to reach out to Microsoft support for further assistance, especially if this is affecting multiple machines in your domain.
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