I go by the rule that if something is not secure enough to plug directly into the Internet, it is not secure. That doesn't mean I'll necessarily do that, but th

I go by the rule that if something is not secure enough to plug directly into the Internet, it is not secure. That doesn't mean I'll necessarily do that, but that should be the bar. The only exception is special purpose backplane networks that are designed explicitly to be isolated. These are basically data busses for clusters, not user-facing networks.