STIG V-253260 - BitLocker Pre-Boot Pin - Windows 11

Welcome to the latest edition of our newsletter, where we provide valuable insights and tips for securing your Windows systems. In this issue, we will focus on the importance of using a BitLocker PIN with a minimum length of six digits for pre-boot authentication on Windows 11 systems.

Implementing a BitLocker PIN with a minimum length of six digits for pre-boot authentication adds an extra layer of security to your Windows 11 systems. It prevents unauthorized access to encrypted drives and ensures the confidentiality of your data, even if an adversary gains physical access to your system.

Encrypting data at rest is crucial for protecting it from unauthorized disclosure. BitLocker PIN serves as a pre-boot authentication mechanism that complements encryption, making it more challenging for unauthorized users to access sensitive information on your Windows 11 systems.

Without a BitLocker PIN or with a weak PIN, your encrypted drives are vulnerable to unauthorized access. An attacker with physical access to your system can bypass operating system controls and compromise the confidentiality of your data. By exploiting the absence or weakness of pre-boot authentication, they can gain unauthorized access to your encrypted drives.

To ensure compliance, verify that the following registry value is configured as specified:

Registry Hive: HKEY_LOCAL_MACHINE

Registry Path: \SOFTWARE\Policies\Microsoft\FVE
Value Name: MinimumPIN

Type: REG_DWORD

Value: 0x00000006 (6) or greater

# Set the vulnerability number
$vulnNumber = "V-253261"

# Set the Working Directory
$WorkingDirectory = "C:\Add\The\Directory\Here"

# Set the file path
$filePath = "$($WorkingDirectory)\$vulnNumber.txt"

# Create or clear the status file
$existingStatusFile = Test-Path $filePath
if (-not $existingStatusFile) {
    New-Item -Path $filePath -ItemType File -Force -Confirm:$false
} else {
    Clear-Content -Path $filePath
}

# Define the vulnerability details
$status = "Open"
$findingDetails = "The required registry value for BitLocker PIN length is not configured as specified."
$comments = "Configure the policy value for minimum BitLocker PIN length."

$minimumPIN = Get-ItemPropertyValue -Path "HKLM:\SOFTWARE\Policies\Microsoft\FVE" `
                                    -Name "MinimumPIN" `
                                    -ErrorAction SilentlyContinue

# EV = Expected Value: Check if the required registry value is configured
$minimumPINEV = 6

if ($minimumPIN -ge $minimumPINEV) {
    $status = "NotAFinding"
    $findingDetails = "The required registry value for BitLocker PIN length is configured as specified."
    $comments = "Not a finding."
}

# Write the variables to the status file
$status         | Set-Content -Path $filePath
$findingDetails | Add-Content -Path $filePath
$comments       | Add-Content -Path $filePath

Powershell Compliance Check Script Explanation:

The provided PowerShell script conducts a compliance check and records the status of the vulnerability assessment. It performs the following actions:

1. Sets the vulnerability number and working directory.

2. Sets the file path for the status file.

3. Creates or clears the status file to ensure a fresh assessment.

4. Defines the vulnerability details, including the status, finding details, and comments related to the vulnerability assessment.

5. Retrieves the current value of the registry entry for BitLocker PIN length.

6. Compares the retrieved value with the expected value to determine compliance.

7. Writes the variables to the status file for documentation purposes.

To ensure compliance with the requirement of using a BitLocker PIN with a minimum length of six digits for pre-boot authentication on Windows 11 systems, follow these steps:

1. Boot into the BIOS (Setup menu) and confirm that the system is in UEFI mode with TPM activated.

2. Under Post Behavior, verify that Fastboot mode is set to Thorough.

3. Boot into the operating system and set up BitLocker on the desired drive, initiating the encryption process.

4. Open the Local Group Policy Editor by launching "gpedit.msc".

5. Navigate to Computer Configuration > Administrative Templates > Windows Components > BitLocker Drive Encryption > Operating System Drives.

6. Double-click on "Configure minimum PIN length for startup" in the right pane to open the configuration window.

7. Choose the "Enabled" option and set the "Minimum characters:" to "6" or greater.

8. Click "Apply" and then "OK" to save the changes in the Group Policy Editor.

Please review and modify the remediation steps as necessary to meet your specific requirements.

# Enable the BitLocker feature if it's not already enabled
Enable-WindowsOptionalFeature -Online -FeatureName BitLocker

# Wait for BitLocker feature to be enabled
Start-Sleep -s 5

# Configure Group Policy for pre-boot authentication
# This sets the policy to allow BitLocker without a compatible TPM and enables the use of a PIN
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\FVE" -Name "UseAdvancedStartup" -Value 1
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\FVE" -Name "UseTPM" -Value 2
Set-ItemProperty -Path "HKLM:\SOFTWARE\Policies\Microsoft\FVE" -Name "UseTPMPIN" -Value 2

# Wait for the Group Policy settings to be applied
Start-Sleep -s 5

# Set the 6-digit PIN for pre-boot authentication
# Replace '123456' with the desired 6-digit PIN
$SecurePin = ConvertTo-SecureString "123456" -AsPlainText -Force
Enable-BitLocker -MountPoint "C:" -EncryptionMethod Aes256 -Pin $SecurePin -UsedSpaceOnly -SkipHardwareTest

# Note: You may need to restart the computer to complete the encryption process.

The provided PowerShell script automates the configuration process to enable a BitLocker PIN with a minimum length of six digits for pre-boot authentication on Windows 11 systems. It performs the following actions:

1. Enables the BitLocker feature if it's not already enabled.

2. Configures the Group Policy settings for pre-boot authentication, allowing BitLocker without a compatible TPM and enabling the use of a PIN.

3. Sets a 6-digit PIN for pre-boot authentication.

4. Encrypts the system drive using the specified encryption method and PIN.

5. Note: Restarting the computer may be required to complete the encryption process.

Please note the following:

• Administrative Privileges: This script needs to be run as an administrator. Save it as a .ps1 file and execute it using PowerShell with administrative privileges.

• Change the PIN: Replace '123456' with the actual 6-digit PIN you want to set.

• Recovery Key: The script will generate a recovery key. Make sure to save it in a secure location.

• Restart: You may need to restart the computer to complete the encryption process and start being prompted for the PIN during pre-boot.

Caution: Modifying system settings, especially encryption settings, can have significant consequences. Make sure to backup any important data before running the script and proceed with caution.

Please review and modify the script as necessary to meet your specific requirements, and make sure to understand each step before executing it.

Implementing a BitLocker PIN with a minimum length of six digits for pre-boot authentication on Windows 11 systems is a critical security measure to protect the confidentiality and integrity of your data at rest. By following the provided remediation steps and utilizing the PowerShell script, you can enhance the security posture of your Windows 11 systems. Regularly validating compliance with BitLocker encryption requirements ensures a robust security foundation.

• Microsoft Docs: BitLocker Drive Encryption Overview

• Microsoft Docs: BitLocker PIN Overview

DISA Cyber: https://public.cyber.mil/stigs/downloads/

Kingdom Dominion Security & Technology: https://www.kdsecntech.com/

Thank you for reading our episode on using a BitLocker PIN with a minimum length of six digits for pre-boot authentication on Windows 11. We hope this information has been helpful to you. If you have any further questions or suggestions, please feel free to reach out. Stay safe and secure!

Kingdom Dominion Security & Technology