best practices to secure ASP.NET Core APIs against modern attacks

Refer these articles for the better understanding

https://www.c-sharpcorner.com/article/best-practices-for-securing-your-asp-net-core-mvc-application/

https://www.c-sharpcorner.com/article/securing-net-core-applications-best-practices-and-techniques/

https://www.c-sharpcorner.com/article/securing-connection-strings-and-appsettings-in-asp-net-core/

Best Practices to Secure ASP.NET Core APIs Against Modern Attacks

1. Use HTTPS Everywhere
   Enforce HSTS and disable weak TLS versions.

2. Strong Authentication & Authorization
   Use OAuth2/OpenID Connect, JWT access tokens, refresh tokens, and role/claims-based authorization.

3. Input Validation & Model Binding Security
   Validate all inputs using FluentValidation/Data Annotations; never trust client data.

4. Rate Limiting & Throttling
   Protect from DDoS, brute force, bot attacks (use ASP.NET Core rate limiting middleware).

5. Secure JWT Handling
   Use short-lived tokens, rotate signing keys, and verify audience/issuer strictly.

6. API Key & Secret Management
   Don’t store secrets in appsettings.json; use Azure Key Vault / AWS Secrets Manager.

7. CORS Hardening
   Allow only specific domains; never use AllowAnyOrigin.

8. Output Encoding & XSS Protection
   Always encode outputs; use proper content types.

9. SQL Injection Protection
   Use parameterized queries and EF Core; block raw SQL from external input.

10. Transport & Data Encryption
    Encrypt sensitive data at rest and in transit.

11. Logging & Monitoring
    Enable structured logging, audit logs, and alerts for suspicious activity.

12. Security Headers
    Apply headers like CSP, X-Frame-Options, X-Content-Type-Options.

13. Zero Trust & Least Privilege
    Limit database permissions, network access, and role privileges.

14. Use Reverse Proxy & WAF
    NGINX/Azure Front Door/Cloudflare to filter malicious requests before API hits.