.NET applications face SQL injection, cross-site scripting (XSS), cross-site request forgery (CSRF), and authentication vulnerabilities. Dot net development address these by implementing input validation, parameterized queries, and data encryption. Using ASP.NET Identity and OAuth 2.0 ensures secure authentication. Role-based access control (RBAC) prevents unauthorized access. Regular penetration testing and static code analysis tools (e.g., SonarQube, Veracode) help detect security flaws. Enabling HTTPS, data encryption, and secure API authentication (JWT, OAuth) further enhances security. Using Azure Security Center and Microsoft Defender for Cloud helps detect and prevent cyber threats in real time.