The Metrics Manifesto

CHAPTER 5Risk Arrival Rates: Shift Left Security Metrics

Probability is expectation founded upon partial knowledge.

— George Boole¹

Introduction: Random Bombs and Horse Kicks

 

The image on the left is of the first ballistic missile. It's called the Vergeltungswaffe 1 (Vengeance Weapon 1, or V-1). During WWII, over 2,300 of them were dropped on London – the impact points are pictured on the right.

A young British actuary by the name of R. D. Clarke was deployed to help analyze hit rates and bombing locations of the V-1. His superiors wanted to know how much of a threat the V-1 posed.² Clarke was tasked with determining if the bombs were landing in random locations – or were they targeted?

Clarke focused on the likelihood of London munitions, rail, and other strategic sites being blown up. Was there anything in the data that revealed a nonrandom pattern? Hits to these sites would be devastating.

For a short and award-winning write-up on this story, read, “The Flying Bomb and the Actuary.”³

Clarke made a grid over the bombed area. Imagine a grid of 576 boxes over the image on the right above.⁴ Each box was a quarter kilometer squared. Some of the boxes would have had one or more dots (bombs) in them. Some would have had zero hits. He then counted up all the hits and ...