Secure Your APIs (Aligned with OWASP Best Practices)

APIs are powerful, they connect apps, services, and users. But with great power comes great responsibility. If APIs aren’t secured properly, attackers can steal data, misuse features, or crash your systems. Here’s a simple guide to secure APIs using techniques aligned with OWASP’s API Security Top 10

1. Use HTTPS – No Exceptions (Covers: API1 – Broken Object Level Authorization, API9 – Improper Asset Management)

HTTPS protects the data in transit. It prevents attackers from listening in or tampering with requests. Whether it’s login info or personal data, always encrypt it with HTTPS.

Tip: Redirect HTTP to HTTPS automatically. Never accept unsecured connections.

2. Use Authentication – Know Who’s Calling (Covers: API2 – Broken User Authentication)

Only let in people or systems you trust. Use tokens (like OAuth2 access tokens, JWTs) to identify callers. If your API is public-facing, use strong authentication (e.g., OAuth with refresh tokens).

Tip: Always expire and rotate tokens. Don’t rely on weak authentication like hardcoded API keys.

3. Enforce Proper Authorization – Don’t Overtrust (Covers: API1 – Broken Object Level Authorization, API5 – Broken Function Level Authorization)

Just because someone is logged in doesn’t mean they can do everything. Check what they’re allowed to access. For example, don’t let a regular user access admin data or another user’s profile.

Tip: Always validate permissions at the object and function level.

4. Validate Inputs – Don’t Trust What You Receive (Covers: API8 – Injection)

Never assume incoming data is clean. Validate all inputs (numbers, strings, IDs, JSON bodies). This protects against injection attacks like SQL injection or command injection.

Tip: Use allowlists for data types and lengths. Sanitize or reject unexpected values.

5. Rate Limiting – Stop Abuse Before It Happens (Covers: API4 – Unrestricted Resource Consumption)

Don’t let one user (or bot) flood your API with requests. Use throttling and rate limiting to block excessive traffic.

Tip: Set limits based on user roles. Block or delay users who go over the limit.

6. Avoid Excessive Data Exposure – Return Only What’s Needed (Covers: API3 – Excessive Data Exposure)

Only send data that’s truly needed for the request. Don’t return internal IDs, secrets, or user info by accident.

Tip: Define and control exactly what each endpoint returns. Avoid generic responses from your database.

7. Use Pagination and Limits (Covers: API4 – Unrestricted Resource Consumption)

Don’t let users download your entire database in one call. Paginate data and set sensible maximums on list endpoints.

Tip: Set a reasonable maxLimit (e.g., 100 or 500). Don’t let clients override it.

8. Don’t Rely on Security by Obscurity (Covers: API10 – Unsafe Consumption of 3rd Party APIs)

Just because something is hidden doesn’t mean it’s safe. Assume attackers can discover your endpoints.

Tip: Always implement proper authentication and authorization, even on “hidden” or “internal” routes.

9. Secure Your API Schema (Covers: API6 – Mass Assignment)

Don’t automatically bind or map incoming JSON directly to your backend models. Attackers can try to add fields they shouldn’t.

Tip: Use DTOs (Data Transfer Objects) or manually control which fields are allowed in a request.

10. Use Centralized Logging and Monitoring (Covers: API10 – Improper Inventory and Logging)

Keep a log of all API activity—especially errors and unusual patterns. This helps catch attacks early.

Tip: Use a security monitoring tool or service. Set alerts for failed login spikes or repeated 404s.

11. Version Your APIs (Covers: API9 – Improper Assets Management)

Old endpoints can become vulnerable over time. Versioning your APIs helps you retire outdated or risky features.

Tip: Include version numbers in your URLs (like /api/v1/orders). Deprecate old versions with warnings.

12. Secure Backend Services Too (Covers: API10 – Unsafe Consumption of 3rd Party APIs)

APIs often call other APIs behind the scenes. Make sure those internal calls are secured, authenticated, and validated.

Tip: Don’t trust third-party services blindly. Validate their responses and sanitize any returned data.

13. Use Proper Error Handling (Covers: API7 – Security Misconfiguration)

Don’t expose stack traces or internal system details in error messages. Keep errors simple and generic for users, and detailed only in logs.

Tip: Return messages like “Invalid request” instead of “NullPointerException in OrderService.java”.

14. Don’t Expose Unused APIs (Covers: API9 – Improper Asset Management)

Disable any old or unused endpoints. The fewer APIs exposed, the smaller your attack surface.

Tip: Run regular API inventory audits to find and shut down anything unnecessary.

Summary:

OWASP gives a solid framework for securing APIs—but you don’t need to be a security expert to follow it. Just remember the basics:

? Authenticate and authorize properly

? Validate everything

? Expose only what’s needed

? Monitor, limit, and log everything

Security isn’t about being perfect—it’s about making it hard enough that bad actors move on to an easier target.