Security reviews fail when they start too late
If the first security conversation happens after the feature is built, every fix feels expensive. A lightweight threat model before implementation can catch the cheap changes.
The useful signal is usually already there.
Security gets real when the trust boundaries light up. Poke it and see what has to hold.
Draw the data flow
Name the actors, data, trust boundaries, secrets, and worst reasonable outcomes. You do not need a perfect diagram to find the scary edges.
A useful threat model creates concrete engineering questions.
Turn threats into tests or controls
The model is only useful if it changes the system: new validation, logging, authorization, rate limits, or a decision not to build the risky path.
Flip the switches and watch the story turn into a tiny operating model.
Make the risk visible early
Threat modeling is not a ceremony. It is a cheap way to avoid discovering the architecture from the breach report.