Probably. I think part of his point is that these days it's very hard to have networks completely isolated from the internet. If there is only one host connecte

Probably. I think part of his point is that these days it's very hard to have networks completely isolated from the internet. If there is only one host connected to both the internet (or a network that connects to it) and that proprietary network, it can act as gateway when compromised and unleash mayhem.