In this video I cover all the steps needed to restrict internet access using group policy. Since this is a user defined policy, you will need to make sure you create an OU specified for the block and add those users there.

The underlying way to block internet using GPO is set an internet proxy pointing to the localhost. Since nothing is configured on the localhost, you are effectively blocking access to the public internet over http and https.

This GPO has been confirmed working on Windows 10, Windows 8, Windows 7 and the policy also works using Server 2016, Server 2012 and Server 2008.

If you have any questions please leave them down in the comments and I'll do my best to get back to you.

Link to Article:
https://thesysadminchannel.com/how-to...