How to Implement Zero-Trust Network Access Principles in Python Code

Zero-trust network access (ZTNA) replaces the outdated assumption that users inside a network are automatically trusted, instead requiring continuous verification on every request. A DEV Community article outlines how engineers can translate ZTNA's three core principles — never trust, least privilege, and assume breach — into working code. The guide demonstrates a FastAPI middleware that validates JWT tokens and calculates a contextual trust score based on factors like token age, IP address, and user-agent headers. Per-resource policy evaluation is also covered, restricting access based on user roles and minimum trust thresholds for each endpoint. Sensitive operations are further protected through step-up authentication, which forces users to re-authenticate even when an active session exists.