In Windows 10 v1607 Anniversary Update there is a brand new UI for sharing your internet connecting and creating a mobile hotspot. The feature has been there in Windows before but has previously required administrative privileges to activate. Starting with Windows 10 v1607 this is exposed in the modern interface under Network > Mobile Hotspot and can be activated as a standard user, posing a security threat if you for instance have network security in place which can then be circumvented.
Using GPO, you can disable Mobile Hotspot in the UI by settings the GPO setting Prohibit use of Internet Connection sharing on your DNS domain network to Enabled. This settings is located under Computer configuration > (Policies) > Administrative templates > Network > Network Connections.
If you are using MDM, you can also configure this with this setting:
URI full path: ./Vendor/MSFT/Policy/Config/WiFi/AllowInternetSharing
Data type: Integer
0 – Do not allow Internet Sharing.
1 – Allow Internet Sharing (default)
Result when this setting is changed wither via GPO or MDM: