APIs, the heart of web development, invite both data breaches and system vulnerabilities if not designed correctly. API security should start not only during the development phase but also during the design phase. In this article, we will explain the best practices for secure API design, while providing example scenarios and solutions. We will also provide backlinks to previous related articles to allow you to examine the topic in depth.

Related Content:

How to Increase Security with Middleware Usage in API Endpoints?
How to Ensure Security When Frontend and Backend Are Served Separately? REST API Communication and Security Guide

1. Principle of Least Privilege

APIs should provide limited information. Data that the user does not need should never be included in the API response.

Example Incorrect Usage:

{
  "id": 1,
  "name": "Ali",
  "password_hash": "$2b$10$7...",
  "email": "[email protected]"
}

Example Correct Usage:

{
  "id": 1,
  "name": "Ali"
}

2. Use Secure Authentication Methods

Instead of weak methods such as basic auth in APIs, modern standards such as JWT or OAuth 2.0 should be preferred.

JWT Example:

const token = jwt.sign({ userId: user.id }, process.env.JWT_SECRET, { expiresIn: '1h' });

3. Prevent Information Leakage in Error Messages

System details should never be given in errors.

Incorrect:

{
  "error": "Database connection failed at dbserver01 with port 3306"
}

Correct:

{
  "error": "A server error occurred. Please try again later."
}

4. Add Rate Limiting and Brute-Force Protection

Limiting requests to the API both prevents service disruption and reduces brute-force attempts.

Example (Node.js Express Rate Limit Usage):

const rateLimit = require('express-rate-limit');
const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 });
app.use(limiter);

5. Perform Data Validation and Sanitization

All data coming to the API must be validated on the backend side.

Example (with Joi):

const schema = Joi.object({ email: Joi.string().email().required() });
const { error } = schema.validate(req.body);

6. Do Not Publish APIs Without Using HTTPS

All API traffic must be encrypted (HTTPS). Unencrypted traffic is vulnerable to sniffing and man-in-the-middle (MITM) attacks.

7. Configure CORS Policies Correctly

Access to all APIs should only be granted to specific domains.

Example CORS Setting:

app.use(cors({ origin: 'https://www.yourwebsite.com' }));

8. Establish Logging and Monitoring Mechanism

Log all API requests.
Integrate a monitoring system that will instantly detect abnormal request bursts.

9. Implement API Versioning

You can separate old endpoints with security vulnerabilities from new endpoints by using versions such as V1, V2.

10. Filter Requests with Middleware Layers

The use of middleware is critical for security. For detailed information, you can take a look at the following article:

How to Increase Security with Middleware Usage in API Endpoints?

Conclusion: Secure Design is a Must for Your APIs

Secure API design is the cornerstone of protecting the privacy of the data and users you are connected to. By implementing the steps we mentioned in this article, you can both ensure security and develop more professional and scalable systems.

For more, be sure to check out our How to Ensure Security When Frontend and Backend Are Served Separately? article.