Reasons for BitLocker Recovery Mode Prompt

BitLocker Recovery Key restores access to a BitLocker-protected device when locked. Since I administer BitLocker via MBAM, I can save the recovery keys to the MBAM Database and Active Directory. In this guide, you will learn the various Reasons for BitLocker Recovery Mode Prompt. I have written tons of articles on MBAM/BitLocker, and I urge you to please take a look at them: How to enable BitLocker AES-XTX 256 Encryption Method, how to correctly disable Microsoft BitLocker Administration and Monitoring encrypted devices. Refer to these articles for more information: Why does MBAM not automatically re-encrypt MBAM or Bitlocker-protected devices, Understanding Microsoft BitLocker Administration and Monitoring Roles, how to Solve the error “Group Policy Settings for BitLocker Startup Options are in Conflict and cannot be applied”, and detailed steps to troubleshoot and fix System Partition not available or large enough [Part 2].

Recovery Key often referred to as a Numerical Password and has a sequence of 48 digits divided by dashes. This technology is designed to protect devices from all offline attacks. Except as described in this link, where a physical attack is possible. I have also described ways to thwart this attack by using “TPM + Pin or TPM with a Password“.

Reasons for BitLocker Recovery Mode

In theory, there are numerous reasons why this window (BitLocker recovery) might be prompted. You will have to troubleshoot specifically to pinpoint what could have happened in your case.

TPM-Related BitLocker Recovery Prompt

For TPM-related issues, one of the following below could cause the BitLocker Recovery Key to be prompted! But not limited to these only.

Table 1 Showing Reasons for BitLocker Recovery

While troubleshooting this device to determine the root cause, one of the following below could have caused the issue. But not limited to these alone.  Below are some reasons why BitLocker could start in recovery mode.

BitLocker asks for a recovery key each time the system boots on USB-C/Thunderbolt systems when docked and undocked

BitLocker Asks for a Recovery Key Every Boot on USB-C/Thunderbolt Computers When Docked or Undocked. Dell has described ways to mitigate this behavior. In some instances (depending on the computer manufacturer and the BIOS), the docking condition of the portable computer is part of the system measurement and must be consistent to validate the system status and unlock BitLocker.

BitLocker prompts you to enter the recovery key when you start a computer from a USB Type-C or Thunderbolt 3 docking station. Note: This issue is only relevant to the following models:

So if a portable computer is connected to its docking station when BitLocker is turned on, then it might also need to be connected to the docking station when it’s unlocked. Conversely, if a portable computer isn’t connected to its docking station when BitLocker is turned on, then it might need to be disconnected from the docking station when it’s unlocked.

How does DELL handle BIOS Update?

This behavior does not apply to all Dell devices when applying updates as the BitLocker Drive Encryption is suspended. I advise to promptly restart.

When the BIOS setup file is downloaded manually, Please check the option “Suspend BitLocker Drive Encryption” as discussed in this guide “how to update the BIOS on your Dell system“.

When will Dell update prompt the BitLocker Recovery Screen?

BIOS-related changes or upgrades. This action only is enough to prompt the BitLocker recovery windows, because when a device is encrypted, it stores the state of the BIOS/UEFI settings thereby causing the boot measurement to change. These changes can cause the BitLocker recovery mode to be prompted!

Dell forgets to enter the switch "/bls" (Bitlocker Supend) for the BIOS installation for a model series. Sometimes, Dell forgets about a series of current catalogs which are used for Update distribution via WSUS.

Note: In the past, you will have to manually suspend BitLocker before updating the BIOS and Firmware updates. This is no longer the case starting with Windows 10 and Windows 11. Modern Windows devices are increasingly protected with BitLocker Device Encryption out of the box and support SSO to help protect the BitLocker encryption keys from cold boot attacks.

The TPM is not involved in any recovery scenarios, so recovery is still possible if the TPM fails boot component validation, malfunctions, or is removed. This is why you could actually protect your device with BitLocker without having a compatible TPM. See this guide “Pre-Boot Authentication: Enable BitLocker without Compatible TPM via the Group Policy“.

To find problematic devices, write a Python script that is capable of querying the MBAM BitLocker Recovery CSV file that has been imported. In this guide, have discussed how to query MBAM to display the report for BitLocker Recovery for a specified period of time. In this same way, you can get the CSV file. Below is a script to query the number of times a device has requested the BitLocker recovery key with the status successful. If you wish to use it, please feel free to reference the link to this guide.

import csv
import datetime
from collections import defaultdict

# Get the current date and time
current_date = datetime.datetime.now()

# Calculate the date two weeks ago
six_months_ago = current_date - datetime.timedelta(weeks=27)

# Open the CSV file
with open("C:\\Users\\xxx\\Desktop\\RecoveryAudit\Recovery Audit Report.csv", 'r') as file:
    reader = csv.reader(file)
    # Skip the header row
    next(reader)
    # Keep track of success events by computer name
    success_by_computer = defaultdict(int)
    total_by_computer = defaultdict(int)
    for row in reader:
        event_date = datetime.datetime.strptime(row[0], '%m/%d/%Y %H:%M:%S %p')
        if event_date >= six_months_ago:
            computer_name = row[5]
            total_by_computer[computer_name] += 1
            if row[2] == "Successful":
                success_by_computer[computer_name] += 1

# Calculate the rate of success for each computer
rates = {}
for computer_name, success_count in success_by_computer.items():
    total_count = total_by_computer[computer_name]
    rates[computer_name] = success_count / total_count

# Print the number of computers that have requested BitLocker recovery keys more than once in the past six months
count = 0
print("Computers that have requested BitLocker recovery keys more than once in the last six months:")
for computer_name, rate in rates.items():
    if rate > 0:
        count += 1
        print("{}: {} times".format(computer_name, int(total_by_computer[computer_name])))

print("Number of computers: ", count)

Summary

This issue could be a result of external factors and not BitLocker itself. Oftentimes, BitLocker will monitor for system configuration changes which could be one of the reasons for the BitLocker Recovery Mode Prompt. When it detects a new device in the boot list or an attached external storage device (USB etc.), the recovery mode (window) could be prompted. But I doubt this is your case. But if this is the case, we have a guide on how to mitigate this by enabling (Thorough) in the BIOS.

I recommended determining the root cause in order to unravel the reason for the BitLocker recovery prompt. This will help in preventing the issue from reoccurring again. kindly check the MBAM Client event logs. This is located in

Event Viewer – Applications and Services Logs – Microsoft – Windows – MBAM - Operational path

Also, the System Event is also paramount in unraveling some BitLocker recovery issues.

I hope you found this blog post helpful. In this guide, you have learned the reasons for BitLocker Recovery Mode Prompt. If you have any questions, please let me know in the comment session.