: Metrics are both fashionable and timely: many regulations that affect cybersecurity rely upon metrics – albeit, of the checklist variety in many cases – to ascertain compliance. However, there are far more effective uses of security metrics than external compliance exercises. The most effective use of security metrics is to manage better, which may include: • Make a business case for needed change • Focus scarce resource on most pressing problems (with the biggest payoff for resolution) • Help spot problems early - or successes early • Address “outside” concerns or criticisms fairly and objectively A successful security metric should: • Motivate good/correct behavior (not promote evasive tactics just to make the numbers look good) • Prompt additional questions (“Why? How?”) to understand what is influencing the numbers • Answer basic questions of goodness (e.g., “Are we doing better or worse?”) • Be objective and measurable, even if correlation may not...