Right, I'm familiar with the hack. My point is Target almost certainly didn't decide that the HVAC firm could be trusted to have access to the credit terminals - the fact that they had access was the result of poor security design, not Target's threat model.
It's the everything always part of the argument that's unreasonable. You realise that that's impossible? You can't vet and control the whole stack. And, if you could, it would be prohibitively expensive.
Ok fair. I see the lack of simple things like segmented vlans as a lack of a threat model entirely. They trusted them implicitly, not explicitly, through their clear incompetence. Perhaps that’s better?
