To fix this problem I cretaed a Group Policy for the users and set an application to run. This replaces explorer.exe with the custom shell application and keeps users from the OS layer.
- Press windows+r and enter ‘mmc’
- File → Add/remove snap in
- Select Group Policy Object from the list on the left and press ‘Add’
- Press ‘Browse’
- Select ‘Users’ tab
- Select the user you will log into from remote machine
- Press OK
- Navigate to User Configuration→Administrative Templates→System
- Enable Custom User Interface and type in your application’s file path. For a custom shell type c:\Path_to_my_custom_shell\MyCustomShell.exe
- Next, go to System\CTRL+ALT+DEL Options and enable Remove Task Manager and all other options if required
When an RDP session is launched and the correct account is logged in to, the application will be run and the user will not be able to send ctrl+alt+del, ctrl+shft+esc or alt+tab to the remote machine.