Good point. Most importantly, that's the far less annoying use-case: one can imagine a simple UX with a list of applications bound to LISTEN on an external inte

Good point. Most importantly, that's the far less annoying use-case: one can imagine a simple UX with a list of applications bound to LISTEN on an external interface for you to whitelist for an hour, a day, or indefinitely. I think browser exploits are still a slightly more common attack vector, but that's certainly an option.