A security system is a combination of equipment, people and procedures. No single component is significantly more important than the other. Unless properly conceived, any changes in the security configuration may have an adverse effect on the other components. Drum Cussac will aim to involve all stakeholders in the production of an Operational Requirement to define: assets to be protected; perceived threats and probability of their occurrence; consequences of compromise of, or damage to, the assets; success criteria and possible outcomes. This is then followed by a focused look at each area of concern to consider individual, possible outcomes.