Best security practices for APIs

Application Programming Interfaces (APIs) have become an integral part of the development world. An API allows one application to communicate with another application. 

April 15, 2022
Martijn van der Put

APIs are primarily used to enhance the functionality of existing applications and add more value for end users. However, with the increasing use of APIs, they have become a focal point for security risks. They are vulnerable to cyberattacks and misuse. In other words, it is now crucial to implement adequate security measures when dealing with APIs. 

Implement authentication

Your APIs should perform authentication before processing any request. Authentication attempts to identify the user or program that sent the request. API authentication typically involves a password, multi-factor authentication, or authentication tokens. Organizations usually use tokens—tokens sent with the request are compared with tokens in the database. This way, requests can be easily tracked.

The OAuth protocol is a widely trusted and used API for user authentication. It also provides administrators with a portal to grant authentication tokens to third parties. Administrators can set custom access rules for each token based on the source of the API request.

Encrypt Requests and Responses

Man-in-the-middle attacks are quite common with APIs. To prevent such attacks, the data traveling between the user and the API must be encrypted. Even if an intermediary intercepts the response or request, the data will be useless without the decryption method.

Encryption for REST APIs can be achieved using the Transport Layer Security (TLS) Protocol or the Secure Socket Layer (SSL) Protocol. However, the SSL and TLS protocols only encrypt the data being transmitted, not the data behind the API. As a result, this sensitive information must be encrypted within the database itself. Use a Web Application Firewall (WAF) with SSL to prevent code injections and DDoS attacks.

Establish API quotas

Brute force attacks, such as DDoS, can be prevented by setting a limit on API calls. You can establish a reasonable limit for the number of API calls the server can receive at any given time. The two main ways to limit API calls are: 

1. Throttling: With throttling, users can still access API data once the limit is reached, but the response rate is reduced. 

2. Quotas: Quotas limit the number of API requests a user can send over time. If the limit is exceeded, the user is denied access. 

Validate all requests

Remember that API requests, even from seemingly reliable sources, can be a breeding ground for potential hackers. Always assume that data is never safe when it comes to APIs. Therefore, always establish rules to determine whether a request is legitimate, harmful, or legitimate but invalid. Proper rules prevent the injection of malicious code into your application. And yes, the API request should only be processed after it passes validation. If not, the request should be prevented from reaching the application's data layer, regardless of how reliable the source appears to be.

Perform security testing

Ensure that your API requests are secure and resistant to all forms of cyberattacks. Take the necessary time and conduct thorough security testing. Engage professional hackers during this phase to test your API and expose it to various vulnerabilities. Moreover, testing is not a one-time process. Continue to perform it regularly, especially after every API update.

Log all activities

So far, we've discussed various ways to prevent your API from being hacked. But what should you do if the API is already compromised? You need a method to trace the source of the problem and report it. Logging all API activities is essential. This will be extremely useful during a breach. It helps understand how the attackers got in, and this valuable information can further strengthen your API security.


When designing your API, follow the above best practices to prevent otherwise avoidable security attacks. Strengthening your API security may require extra effort and time, but it is worth it to protect sensitive data on your server. It will help build trust with your end users.


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