Windows Security Log Event ID 4909

4909: The local policy settings for the TBS were changed

On this page

• Description of this event
• Field level details
• Examples
• Mini-seminars on this event

This event, 4909, is apparently logged when you make a change to the TPM configuration in the local policy object of the computer as opposed to GPOs in Active Directory (see event 4910).

TPM Base Services (TBS) proves an interface to the Trusted Platform Module chip in the computer if so equipped. BitLocker Drive Encryption is the most prominent feature of Windows that uses TPM.

TPM commands are referred to as ordinals.  MSDN: "To preserve integrity of operations, certain TPM commands are not allowed to be executed by software on the platform. For example, some commands are only executed by system software."  

Old Blocked Ordinals: TPM commands blocked before this event
New Blocked Ordinals: TPM commands blocked after this event

I haven't been able to produce this event. Have you? If so, please start a discussion (see above) and post a sample along with any comments you may have! Don't forget to sanitize any private information.

Free Security Log Resources by Randy

• Free Security Log Quick Reference Chart
• Windows Event Collection: Supercharger Free Edtion
• Free Active Directory Change Auditing Solution
• Free Course: Security Log Secrets

Description Fields in 4909

• Old Blocked Ordinals: %1
  
• New Blocked Ordinals: %2

Supercharger Free Edition

Your entire Windows Event Collection environment on a single pane of glass.

Free.

 

 

Upcoming Webinars Assessing the Security of Your Active Directory: User Accounts Anatomy of a Cloud Hack: The Cloudflare/Okta Compromise – A Story of Tokens, Lateral Movement, Persistence and the Salvation of Zero Trust and Hard MFA Tokens

Additional Resources

•	Event IDs
•	All Event IDs
•	Audit Policy