A fundamental analysis of crime and the juridical systems to punish crime has yielded a starting point for quantitative risk analysis of security risks. This method is called the MMO concept as a generic concept for the design of security barriers and their evaluation by quantitative risk analysis methods. It is based on a simplification of the basic elements for proving criminal liability that a defendant committed a crime under US law: motive, means and opportunity. These three elements form the preconditions that are needed to let an ill meaning person to develop into a hazard or threat. The MMO concept also forms the key to the development of successful barriers against the completion of the actual act. Taking one of these three away would render the hazard ineffective. This enables the development of a model for security threats along the same lines as safety threats and opens the possibility for similar qualitative and quantitative analysis. The MMO concept may seem relatively straightforward but the derivation of the theoretical foundation is not simple.