> The saying that stuck with me was "defenders have to be right 100% of the time, while attackers only have to be right once".

> You are suggesting this isn't correct?

The intuition behind that is applicable only when correctness is stochastic. If you need to be waved in by a security guard, then one fake mustache might be the difference between being granted or denied entry. However, a keypad either works or it doesn't; entering the wrong PIN is guaranteed refusal.

The other breach of that intuition is defense in depth. Secure systems don't generally rely on a single binary trusted/untrusted status; the classified building still locks its interior doors. This is the part that has – in my view temporarily – changed most with frontier models, in that they are much more skilled at chaining together vulnerabilities than previous models (and much faster about it than human experts, even if potentially less skilled). If a system has a latent (0-day) vulnerability 50% of the time, then 10 independent layers would imply a ≈ 1/1000 chance that a critical compromise is possible.

However, these independent layers don't currently happen in practice because it's easier to write insecure code than secure code. With luck, modest discipline, and defensive use of frontier models I think that this gap will narrow with time, in much the same way that it would be plainly crazy to deploy root access via telnet today.