Information
This policy setting determines whether or not the user can interact with Cortana using speech while the system is locked.
The recommended state for this setting is: Disabled
Access to any computer resource should not be allowed when the device is locked.
Solution
To establish the recommended configuration via GP, set the following UI path to Disabled :
Computer Configuration\Policies\Administrative Templates\Windows Components\Search\Allow Cortana above lock screen
Note: This Group Policy path is provided by the Group Policy template Search.admx/adml that is included with the Microsoft Windows 10 Release 1607 & Server 2016 Administrative Templates (or newer).
Impact:
The system will need to be unlocked for the user to interact with Cortana using speech.