Resolving High Authentication Errors Caused by Monitoring Tools in a Domain Environment

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Applies To:

1. Environments using agentless monitoring tools (e.g., LRE, SiteScope, custom monitoring solutions)
2. Systems integrated with domain-based authentication (e.g., Active Directory)
3. Any monitoring setup that uses stored domain credentials for resource polling

Issue:

A monitoring server triggered an extremely high volume of authentication errors — reaching over 300,000 failed logins per hour — directed at domain controllers. This caused significant performance issues across the authentication infrastructure, leading to high resource usage on the domain controllers and increased risk of service disruption.

Attempts to access the monitoring system’s UI to investigate were blocked due to missing client software and certificate issues.

Cause

The root cause was found to be invalid or outdated credentials stored in the monitoring tool. These credentials were repeatedly used by multiple scheduled monitors, each attempting to authenticate and failing continuously.

This created an authentication storm, severely overloading the domain controllers.

Steps

1. Verify Monitoring Service State
   • Check if the monitoring service is running. In this case, it was already stopped to reduce impact.
2. Attempt to Access the UI
   • Try to access the monitoring UI to inspect credentials.
   • If inaccessible due to missing software (e.g., Java client) or certificate errors, proceed to an alternate method.
3. Use an Offline Tool to Modify Credentials
   • Utilize a configuration-level tool (e.g., a persistency viewer or config file editor) to update the stored domain account password used in monitors.
4. Restart Monitoring Service
   • Start the monitoring service after updating credentials.
   • Confirm from logs that:
     • The service starts successfully.
     • Monitors are running without errors.
     • No authentication failures are recorded.
5. Confirm with Identity Team
   • Have the authentication/infrastructure team check domain controller logs to confirm that the error volume has dropped and that the service account is authenticating successfully.
6. Establish a Baseline (Optional)
   • To validate the fix, stop the monitoring service temporarily (e.g., for 48 hours) to observe if the authentication traffic stabilizes.
   • Restart the service after the baseline period and monitor for any recurrence of the issue.

Additional Info:

1. Always validate stored credentials after password changes or account policy updates.
2. Use dedicated service accounts for monitoring with limited privileges.
3. Keep alternate access options available in case the monitoring UI becomes inaccessible.
4. Set alerts on domain controllers to detect authentication spikes early.

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