Shipping Secure APIs: Threat Models and Tests

Shipping secure APIs means designing, building, and testing interfaces with security in mind from day one. APIs connect teams, partners, and customers, and a weak point can expose data or undermine trust. The goal is to map possible attacks against your API surface and verify that defenses work in real life.

Threat modeling: a lightweight approach

A practical start is to ask three questions: what are we protecting, who might attack, and where can attackers reach us? Make a quick list of data, users, and services, then map endpoints, webhooks, and queues. Use a simple STRIDE lens to spot risks: Spoofing, Tampering, Information disclosure, Denial of service, and Elevation of privilege. This helps teams discuss risks without heavy tooling.

Common API threats

  • Broken authentication and session management
  • Excessive data exposure in responses
  • Insecure direct object references and ID leakage
  • Missing or weak authorization checks
  • Rate limit bypass and abuse
  • Security misconfig and secret leakage
  • Injection and insecure deserialization
  • Inadequate logging and monitoring

Tests to cover secure APIs

Testing should cover design, code, and runtime behavior. Key areas include:

  • Access control tests, especially object-level authorization
  • Authentication and token validation tests (expiry, rotation, revocation)
  • Input validation and protection against injection
  • Data minimization: verify responses don’t leak sensitive fields
  • Rate limiting and abuse protection tests
  • Error handling: avoid revealing internal details
  • Secrets management: ensure no secrets appear in responses or logs
  • Automation: integrate tests into CI, run contract tests and fuzz tests on every PR

Practical steps you can take

  • Add threat modeling reviews in design reviews for new APIs
  • Create lightweight security tests that mirror real use, not just theory
  • Use OpenAPI contracts to validate responses and error formats
  • Run automated checks in CI and fail builds on serious findings
  • Monitor runtime behavior to catch anomalies early

By tying threat modeling to concrete tests, you can ship APIs that are safer by default and easier to maintain. A steady rhythm of design reviews, automated tests, and monitoring builds lasting trust with users and partners.

Key Takeaways

  • Start with a simple threat model that covers actors, data, and endpoints
  • Test both design and runtime: access control, token handling, and data exposure
  • Automate security checks in CI and keep monitoring ongoing