What is Threat model? Definition and explanations
A threat model is the structured analysis that answers four questions: what are we building, what can go wrong, what are we going to do about it, and did we do a good enough job. You describe the system, identify threats by category — spoofing, tampering, disclosure, denial of service — then decide which countermeasures are worth their cost. It belongs at design time.
In one sentence
A threat model identifies what can go wrong in a system, from the design stage.