"How do we ensure people build secure systems?"
This was the question to the panel before mine at the Thayer School's Complex Systems Symposium. It's not a new question - it comes up every time anyone tries to tackle hard problems around internet security. But it's an unfair question, because we have never built anything securely.
The question was asked in a lecture hall. Every time the symposium took a break, the two aisles bottled up with side conversation, inhibiting the flow of people needing to exit/enter. There were several "captains of industry", extremely talented professors, and bright students in the room; yet a mob could have swooped in shouting at any minute or an attacker could have waltzed in unimpeded (I could go on and on with threat scenarios). Yet who is responsible for the poor security design of that lecture hall?
In reality, security is about making good risk decisions, and accepting that there are some attacks and adversaries that you will not defend against. For internet-connected systems, this tradeoff is harder, as the cost to your adversaries is usually small enough that attacks that are implausible in the physical world become economical (remember the half-penny skimmers?)