Hi there,
a similar topic in regards to the “update” functionality was handled here: PPT50 Update function doesn't require password
Since that functionality can now be blocked, what other reason is there to disable the interface compeltely?
Anyway, if that’s still needed, I recommended “usb port lock” here: PPT50 Update function doesn't require password - #4 by michael_w and would apply the same solution to your issue 
Best regards