Detections
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18.9.11.2.17 (BL) Ensure 'Require additional authentication at startup' is set to 'Enabled'

Information

This policy setting allows you to configure whether BitLocker requires additional authentication each time the computer starts and whether you are using BitLocker with or without a Trusted Platform Module (TPM). This policy setting is applied when you turn on BitLocker.
Note: Only one of the additional authentication options can be required at startup, otherwise a policy error occurs.
If you want to use BitLocker on a computer without a TPM, select the 'Allow BitLocker without a compatible TPM' check box. In this mode a USB drive is required for start-up and the key information used to encrypt the drive is stored on the USB drive, creating a USB key. When the USB key is inserted the access to the drive is authenticated and the drive is accessible. If the USB key is lost or unavailable you will need to use one of the BitLocker recovery options to access the drive.
On a computer with a compatible TPM, four types of authentication methods can be used at startup to provide added protection for encrypted data. When the computer starts, it can use only the TPM for authentication, or it can also require insertion of a USB flash drive containing a startup key, the entry of a 4-digit to 20-digit personal identification number (PIN), or both.
Users can configure advanced startup options in the BitLocker setup wizard.
Note #2: If you want to require the use of a startup PIN and a USB flash drive, you must configure BitLocker settings using the command-line tool manage-bde instead of the BitLocker Drive Encryption setup wizard.
The recommended state for this setting is: Enabled.

Rationale:
TPM without use of a PIN will only validate early boot components and does not require a user to enter any additional authentication information. If a computer is lost or stolen in this configuration, BitLocker will not provide any additional measure of protection beyond what is provided by native Windows authentication unless the early boot components are tampered with or the encrypted drive is removed from the machine.

Solution

To establish the recommended configuration via GP, set the following UI path to Enabled:
Computer Configuration\Policies\Administrative Templates\Windows Components\BitLocker Drive Encryption\Operating System Drives\Require additional authentication at startup
Note: This Group Policy path may not exist by default. It is provided by the Group Policy template VolumeEncryption.admx/adml that is included with the Microsoft Windows 7 & Server 2008 R2 Administrative Templates (or newer).

Impact:
A PIN requires physical presence to restart the computer. This functionality is not compatible with Wake on LAN solutions.

Default Value:
Disabled. (Users can configure only basic options on computers with a TPM.)

References:
1. CCE-33103-3

See Also

https://workbench.cisecurity.org/benchmarks/14249

Item Details

Category: IDENTIFICATION AND AUTHENTICATION, SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|IA-5c., 800-53|SC-28(1), CSCv6|16.1, CSCv7|16.3

Plugin: Windows

Control ID: c71b89d305ae2d068842107be785688bd598ca52858ecb768cd6d6a53375e7b5