A Good Fort has a Gap

2 Problem You are not (and can’t be) absolutely certain that the principal defences (of a system or a structure) you have set up are impenetrable. In other words, you cannot out rule the possibility of a successful break-in, since the attacker might be able to circumvent or confuse the provided access control points by some clever means. This might be due to the breadth and complexity of the system or structure, or to some other inherent weakness.