How to troubleshoot 521 Events in Security Log

[KoopKB]

I am getting a slew of Event 521 in the WIndows Security Log on about half my DCs. they are triggering Critical Alerts in ADAudit, so I need to determine the cause and resolve it. So far, I have

• Rebooted the DC
• Confirmed adequate disk space
• Confirmed permissions on the .evtx file
• Cleared the Security Log
• Deleted and re-create the Security .evtx file
• Set Log size to 1GB
• Enabled AutoArchive of the Logs
• Set Security Log BufferSize=256 and MaxBuffers=64

Any suggestions on how to troubleshoot this are greatly appreciated.

 

[ChatGPT]

It appears you've repeated your query about troubleshooting Event 521 in the Windows Security Log. I’ll provide a more flesh-out and tech-savvy approach to tackle this ongoing issue.

Advanced Troubleshooting Steps for Event 521​

1. Double-Check Log Retention Settings: Make sure that your auto-archive settings are functioning properly and logs are not being deleted before they can be processed. Sometimes archive settings can inadvertently cause logs to miss entries.
2. Investigate Event Source: Query the event log for information about which process or service is generating the Event 521 entries. This can sometimes give a direct lead on where to focus your attention.
3. Inspect System Resources: Despite confirming adequate disk space, ensure that CPU and memory resources are also sufficient on the affected DCs. Heavy resource usage can lead to issues in handling log files.
4. Examine DC Health: Run a diagnostic on your DCs using the dcdiag command to ensure that domain controllers are functioning correctly. Look for any warnings or errors, especially those related to Active Directory replication.
5. Review Network Configuration: Ensure there are no network issues between your DCs and clients that could be causing logging delays or failures.
6. Explore Security Configuration Settings: Look into the Advanced Audit Policy settings in Group Policy. Check if anything is misconfigured or redundant, which can lead to excessive events being logged.
7. Look into Application and System Logs: Check to see if there are any corresponding errors in the Application or System logs that might provide insights into other underlying issues affecting your security logs.
8. Review Installed Software: Consider whether any recently installed software or updates could be interfering with normal logging operations. This includes security agents, monitoring solutions, or backup tools.
9. Use Windows Sysinternals: Leverage tools like Procmon (Process Monitor) from Sysinternals to identify processes accessing the security logs or related resources during the periods when Event 521 occurs.
10. Consider Active Directory Auditing Limitations: If you have many login attempts (successful or failed) by users or services, you may be overwhelming the logging capability of your DCs. Address these activities if applicable.
11. Potential Misconfiguration in ADAudit: Since ADAudit is triggering critical alerts, look into its configuration settings as well. Check if there's an unusual log scanning frequency or configuration that might be causing the events.
12. Run Event Tracing for Windows (ETW): As a more advanced step, you can use ETW for performance monitoring to capture detailed information about what’s occurring when the event is logged.

If these approaches don’t yield results, it may also be beneficial to capture specific Event IDs around the time of the Event 521 occurrences and correlate them. Sometimes, the sequence of events can yield clues that aren't readily apparent. Good luck, and keep us updated on any progress or new findings!

 

[Neemobeer]

Depending on how much you are auditing and how many systems there are you may just need to keep bumping the log size and buffers or tune down what you are auditing.

 

[ChatGPT]

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