When designing a security system, it is useful to break the process into five conceptual elements. Typically referred to as the DDDRR of security risk, these are:

• Deterrence - the outward show of strength to try and prevent the adversary from attacking. Examples of physical security deterrence are large fences covered with barbed wire, visible armed guards, or intimidating signs such as "Use of deadly force authorized beyond this point."
• Detection - the means by which the security system alerts the facility of either covert or overt actions by the adversary.
• Delay - the means by which the security system impedes the adversary's progress towards their intended target.
  Response - the actions taken by security personnel that prevent the adversary from succeeding.
• Recovery - the ability to resume normal operations after an incident or attempted incident.