TPM locked out only early in the morning
Posted on 2013-06-13
I have an HP Folio 9470m ultrabook that is causing some grief with BitLocker for one of our users who routinely comes into the office at 6:00 AM. He attempts to log in using his BitLocker PIN and is notified that his password has been attempted too many times. If I try to recreate this issue when I get into the office at 8:00 AM, I am unable to do so and everything works fine. So this morning I decided to come in bright and early with him just to see this first hand. What I've confirmed is that it does in fact seem as though the TPM is in a lockout mode. BitLocker will not accept the PIN and states that a password has been attempted too many times. I am able to bypass the PIN using a recovery key and boot to Windows, but when I attempt to launch the BitLocker management console, I receive an error that "the TPM is defending against dictionary attacks and is in a time-out period".
After doing a bit of reading up on this, I've found that this error message indicates that the TPM is in lockout, and that the only way to unlock is via the TPM Administration console, or by logging onto Windows using a recovery key and leaving the computer powered on for 20 hours.
So my question is this: Why is this only happening at 6:00 AM everyday and then appears to be fine when we check things out at 8:00 AM?
Does anyone have any thoughts on this?