Do you know what all security documents have in common? — they all were at some time called “threat model”… A joke indeed, and not the funniest one, but here to make a point. There is no one approach to threat modelling, and not even a single definition of what a threat model really is. So what is it? It is most often considered to be a document that introduces the security needs of a system, using any one of dozens of possible approaches. Whatever the modelling approach is, the threat model really has just one strong requirement: it needs to be useful for whatever purpose it is made to serve. Let us try to describe what we often try to get from a threat model, and how to achieve it.Continue reading "Useful threat modelling"