STRIDE Threat Modeling: A Step-by-Step Guide

What if you could systematically find security flaws before attackers do?

That's exactly what threat modeling delivers. And STRIDE is the methodology that's helped security teams do it consistently for over two decades. Developed at Microsoft in 1999, STRIDE provides a structured framework for identifying threats that maps directly to the security properties you're trying to protect.

In this guide, you'll learn how to apply STRIDE to your systems—whether you're securing an API, a microservices architecture, or preparing for a compliance audit.

What is STRIDE?

STRIDE is a threat modeling methodology that categorizes security threats into six types. Each category maps to a security property that attackers try to violate:

The power of STRIDE is its simplicity. For every component in your system, you ask: "How could an attacker spoof, tamper, repudiate, disclose, deny service, or elevate privilege here?"

A Brief History

STRIDE was created by Loren Kohnfelder and Praerit Garg at Microsoft to help developers think systematically about security threats. It's since become one of the most widely used threat modeling frameworks, incorporated into tools like Microsoft's Threat Modeling Tool and OWASP Threat Dragon.

When to Use STRIDE

STRIDE works best in these scenarios:

During Design (Ideal)

Threat modeling during the design phase catches issues when they're cheapest to fix. Before you write code, map out your architecture and run STRIDE against it.

On Existing Systems

Already in production? STRIDE still helps. Focus on critical components, data flows, and recent changes. You'll likely find issues that testing alone would miss.

For Compliance

Regulations like DORA, ISO 27001, and SOC 2 require documented risk assessments. A STRIDE threat model provides the systematic, auditor-ready documentation they expect.

Before Major Changes

Adding a new API? Integrating a third-party service? Moving to the cloud? These are ideal moments to revisit your threat model.

Step-by-Step: How to Apply STRIDE

Step 1: Define the Scope

Start by answering: What are we protecting?

Don't try to model your entire organization at once. Pick a specific system, application, or feature. Good starting points:

Step 2: Create a Data Flow Diagram (DFD)

Map how data moves through your system. A DFD includes:

┌─────────────┐     HTTPS      ┌─────────────┐     SQL      ┌─────────────┐
│    User     │ ─────────────► │   Web API   │ ──────────► │  Database   │
│  (Browser)  │                │  (Process)  │              │   (Store)   │
└─────────────┘                └─────────────┘              └─────────────┘
       │                              │
       │         Trust Boundary       │
═══════╪══════════════════════════════╪═══════════════════════════════════
       │           (Internet)         │

Step 3: Identify Threats Using STRIDE

Now walk through each component and data flow, asking the STRIDE questions:

For each process, data store, and data flow:

Example findings for a Web API:

Step 4: Prioritize with Risk Assessment

Not all threats are equal. Prioritize based on:

Many teams use DREAD scoring alongside STRIDE:

Focus your mitigation efforts on high-risk threats first.

Step 5: Define Mitigations

For each prioritized threat, define how you'll address it:

Step 6: Document and Track

Your threat model isn't useful if it lives only in someone's head. Document:

Store this alongside your architecture documentation. Review it when the system changes.

Common STRIDE Mistakes to Avoid

1. Doing it once and forgetting it

STRIDE isn't a one-time exercise. Your system evolves, new threats emerge. Review your threat model quarterly or when making significant changes.

2. Scope too broad

Trying to model everything leads to analysis paralysis. Start small, go deep, then expand.

3. Ignoring trust boundaries

The most interesting threats happen where trust levels change—between the internet and your app, between services, between user roles. Pay extra attention here.

4. Skipping the DFD

It's tempting to jump straight to listing threats. Don't. The DFD forces you to understand your system systematically. Threats become obvious once you see the data flows.

5. Not involving developers

Security teams can't threat model in isolation. Developers know how the system actually works—including the shortcuts and workarounds that create vulnerabilities.

Tools for STRIDE Threat Modeling

Free:

Commercial:

AI-Assisted:

Key Takeaways

Next Steps

Ready to threat model your system but short on time? Our AI-powered platform delivers expert-reviewed threat models in days, not weeks.

Get started with Ansvar and see how systematic threat identification can strengthen your security posture.

Sources: