The API Security Checklist: 10 Best Practices to Protect Your Endpoints Right Now

The Foundational Pillars of API Security 🛡️

API security requires a defense-in-depth strategy, addressing threats at the perimeter, the transport layer, and the application logic layer. This action-oriented checklist focuses on the ten most impactful best practices you can implement immediately to drastically reduce your attack surface.

1. **Implement an API Gateway:** Establish a single **Policy Enforcement Point** to centralize Authentication, Rate Limiting, Throttling, and consistent logging. This is the foundation of scalable security.
2. **Enforce BOLA Checks (The #1 Priority):** Mandate that every API endpoint that accesses a resource (read, write, delete) must verify the authenticated user ID is the authorized owner or has the required relationship to the object.
3. **Use JWTs/OAuth 2.0:** Retire simple, static API keys for user-facing APIs. Use signed, time-limited **JWTs** for stateless identity propagation and **OAuth 2.0** for secure access delegation.
4. **Apply Granular Rate Limiting:** Protect all endpoints, especially login and password reset, using intelligent rate limiting based on the **User ID** (if authenticated) or a combination of Client ID and IP address.
5. **Validate All Input:** Never trust client-side data. Enforce strict **schema validation** (type, length, format) on all request bodies, headers, and query parameters to prevent injection attacks and logic abuse.
6. **Avoid Excessive Data Exposure:** Use dedicated **DTOs (Data Transfer Objects)** to strip all sensitive, internal, or unnecessary fields from the JSON response before transmission.
7. **Enforce a Zero Trust Network:** Use **mTLS (mutual TLS)** for all communication between microservices to ensure both encryption and verified service identity, even within the internal network.
8. **Document and Manage API Inventory:** Use tools and the API Gateway to continuously monitor traffic and ensure all actively used endpoints are documented, secured, and included in the security review process (preventing Shadow and Zombie APIs).
9. **Use Strong Logging & Monitoring:** Log all security-relevant events—especially **authorization failures (403)**, **authentication failures (401)**, and **rate limit hits (429)**. Feed these logs into a SIEM for real-time attack detection.
10. **Implement Transport Layer Security (TLS):** Mandate **HTTPS** and enforce strong TLS protocols (TLS 1.2 or higher) with strict HSTS (HTTP Strict Transport Security) policies to prevent all man-in-the-middle attacks and downgrade attempts.