Threat Modeling a Real System

How to systematically find the security gaps in a whole system - not one vulnerability at a time, but by drawing the data flows, marking trust boundaries, and working through STRIDE against a real example: a file-sharing app with uploads, accounts, and payments.

1. Drawing the System How to draw a data-flow diagram of a real application and mark its trust boundaries - the setup every STRIDE pass depends on.
2. STRIDE, Applied Walking each STRIDE category against a real app's trust boundaries - concrete findings on the file-sharing example, not abstract definitions.
3. From Threats to Action Prioritizing threat-model findings by real risk, turning them into concrete fixes, and being honest about what threat modeling doesn't replace.