18.9.11.1.1 (BL) Ensure 'Allow access to BitLocker-protected fixed data drives from earlier versions of Windows' is set to 'Disabled'

Information

This policy setting configures whether or not fixed data drives formatted with the FAT file system can be unlocked and viewed on computers running Windows Server 2008 (non-R2), Windows Vista, Windows XP with Service Pack 3 (SP3), or Windows XP with Service Pack 2 (SP2) operating systems.
Note: This policy setting does not apply to drives that are formatted with the NTFS file system.
The recommended state for this setting is: Disabled.

Rationale:
By default BitLocker virtualizes FAT formatted drives to permit access via the BitLocker To Go Reader on previous versions of Windows. Additionally the BitLocker To Go Reader application is applied to the unencrypted portion of the drive.
The BitLocker To Go Reader application, like any other application, is subject to spoofing and could be a mechanism to propagate malware.

Solution

To establish the recommended configuration via GP, set the following UI path to Disabled:
Computer Configuration\Policies\Administrative Templates\Windows Components\BitLocker Drive Encryption\Fixed Data Drives\Allow access to BitLocker-protected fixed data drives from earlier versions of Windows
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:
Fixed data drives formatted with the FAT file system that are BitLocker-protected cannot be unlocked on computers running Windows Server 2008 (non-R2), Windows Vista, Windows XP with SP3 or Windows XP with SP2. BitLockerToGo.exe will not be installed.

Default Value:
Enabled. (Fixed data drives formatted with the FAT file system can be unlocked on computers running Windows Server 2008 (non-R2), Windows Vista, Windows XP with SP3 or Windows XP with SP2, and their content can be viewed. These operating systems will only have read-only access to BitLocker-protected drives.)

References:
1. CCE-34253-5

See Also

https://workbench.cisecurity.org/files/2754