Trust Boundaries & Attack Surface Reduction
Learn to identify trust boundaries in a system, map the attack surface, and apply techniques to shrink it as a core part of secure design.
What Is a Trust Boundary?
A trust boundary is any point where data or control crosses between zones of different trust levels. Examples include the line between the public internet and your API gateway, or between your application and a third-party service.
Every time data crosses a boundary, you must validate and authorize it. Insecure design often comes from assuming data inside a boundary is automatically safe.
Why Boundaries Matter
Attackers exploit the assumption that internal callers are trustworthy. If a microservice trusts another service blindly, a single compromised node can pivot across your whole system.
- Treat each boundary crossing as a fresh validation point
- Never reuse trust from one layer to skip checks in another
- Document boundaries explicitly in your architecture
All lessons in this course
- Principles of Secure Design
- Practical Threat Modeling
- Secure Architecture Patterns
- Trust Boundaries & Attack Surface Reduction