Long story short, I'm searching for a tool or config that blocks all network traffic except whitelisted ones and works without a own proxy.
In my institution every device that wants to connect to the internet requires proxy configuration. Therefore we have a central squid server running.
Now I wanted to create a save exam environment, where network functions are limited to 1-2 whitelisted domains. Since the used PCs vary or students can bring the own device, I can't hardcode the IP adresses in the central squid. So I'd like to realize this with a custom Ubuntu live usb drive.
The first idea that came to my mind was a filter tool like DansGuardian. However, these tools I found all require their own local squid to work. But as you remember, there's already one in use that can't be bypassed.