Secure software requires both design-time and code-time protection. STRIDE threat modeling helps identify risks early in system design, while SonarQube enforces secure coding practices through static analysis. Together, they provide a practical, end-to-end approach to building secure applications. In this article, you'll learn how to apply STRIDE threat modeling and SonarQube static analysis to identify, prevent, and fix security vulnerabilities in modern applications. Table of Contents Why Security Must Be Built In, Not Added Later Prerequisites Understanding STRIDE Threat Modeling Applying STRIDE Step-by-Step Introduction to SonarQube How SonarQube Enhances Security Bridging STRIDE and SonarQube Practical Example: Securing a Login API Best Practices for Secure Development Common Challenges and Limitations When NOT to Rely Solely on These Tools Future Enhancements Conclusion Why Security Must Be Built In, Not Added Later Modern applications handle sensitive data, user identities, and critical business…