STRIDE

What it means

STRIDE is a checklist for finding threats when you design a system, by asking six standard questions about each part of it. Its six letters are Spoofing, Tampering, Repudiation, Information disclosure, Denial of service and Elevation of privilege. Microsoft created it, and it is still among the most used methods for threat modelling.

Each letter is the opposite of a good property that you want the system to keep. Spoofing breaks authentication, tampering breaks integrity, repudiation breaks accountability, disclosure breaks confidentiality, denial of service breaks availability, and elevation of privilege breaks authorisation. Walking through all six covers the ground in a repeatable way.

Why it matters

Teams that skip a structured method tend to find the threats they already know. STRIDE prompts you to ask six different questions of each part of the design, so gaps in less obvious areas get noticed, such as a missing audit trail or a part anyone can overload.

Finding these at the design stage is cheap. A missing check caught on a diagram costs a conversation. The same gap found in production can mean data exposure, a service outage or a record nobody can trust. It gives security and engineering a shared vocabulary.

How it shows up

The usual method is to draw a data flow diagram showing users, services, data stores and the lines between them, then go through each element with the six letters. For each match, you write down the threat, how likely it is, and what limits it. Findings become security requirements or tasks.

The mistakes repeat. The diagram is too vague to reveal anything. Everything is listed and nothing ranked. Or the exercise is done once and never revisited as the system changes. Keep sessions short, focus on trust boundaries, and repeat when the design changes. Pair it with a ranking step to decide what to fix first.