Vulnerability assessment analysis is a method of identifying the weak points of your client and/or principal. What makes them vulnerable? Is your protectee susceptible to risk? If so, what are the consequences if a vulnerability is exploited? A vulnerability assessment must be performed to establish some sort of baseline of security effectiveness against the threats assessed. You must verify the effectiveness of your defense and then you must make sure that whatever process you choose is performing as required.
Detection can be defined as the discovery of overt or covert action by an adversary. If you detect a vulnerability, who is it? and why are they doing it? The who's and why's might be easy or difficult depending on the circumstances. The intrusion might come from a computer source (cybersecurity) or a physical source (physical security). Once you detect the vulnerability how can the attack occur. This might be an arduous task being that attacks can occur from a great many locations. Go through them all from the eyes of an adversary. Take every egress and ingress routes. I personally like to take the movement of a protectee and then formulate attack plans from those movements. This could be sitting in an office, moving to a meeting space or entertainment venue, traveling in a vehicle. If your protecting trade or proprietary secrets then cybersecurity or technical surveillance counter measures are necessary.
Delay refers to slowing down an adversary's progress. You can accomplish delays through security barriers This might be access control, alarm systems, or security personnel. This could be the security features added to a computer system. How much time would it take to bypass a security system? or how could someone bypass a system? Red teaming is a good way to assess the delay efforts. If a delay occurs before a detection we would call that a deterrent. Your goal is to make your protectee a hard target. If you are a solo operator only, then your mind and the collaboration with your protectee is the best defense. Secrecy, change of movement, disguise of protectee, misdirection of information, no movement at all, these are just examples of delaying an attack on the protectee. If the principal's whereabouts or schedule is unknown they cannot be attacked.
Lastly, you must respond with dominance. Dominate the situation. It is not enough that you take action. The action you take must be a victory for you and your client/ principal. You must be in the right position at the right time in order to stop the adversary's progress. The response is measured from the time the vulnerability information was received to the time of the interruption of the adversary's actions. If there is a lack of response to an attack on a vulnerability and no detection of intrusion then the vulnerability assessment was a fail.
Always stay safe and vigilant.