Nope. You just flipped one of your caveats: no internet connectivity. I only specified networking. Its also how Target was attacked. Their registers are netwo

Nope. You just flipped one of your caveats: no internet connectivity. I only specified networking. Its also how Target was attacked. Their registers are networked yet there was a hole from the internet to their corporate net. That hole was through their HVAC control system. The Tl;Dr. Is that you design a secure system, so that if one part fails, the whole system doesn't fall like a house of cards. Security through layers.