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REST API Security Comprehensive Guide

Kay James
January 16, 2024 | 11 min read

API development has skyrocketed in recent years, propelled by digital transformation and the critical role APIs play in both mobile apps and IoT. Because of this expansion, API security has become a primary priority.

In this article, we will learn about REST APIs, their security, and why they are important. We will also cover how to protect your REST API and common API threats.

What is a REST API?

The REST API, or Representational State Transfer Application Programming Interface, is a mechanism for accessing online services using HTTP requests to obtain, change, and remove data. It depends on the REST architectural style, which is differentiated by its capacity to send resource representations between systems while retaining no server context between requests. In other words, each request has all of the information required to execute the operation. As a result, REST API is an essential component of current web design, allowing data interchange between online apps and mobile devices.

What is API Security?

An API (Application Programming Interface) allows software programs to exchange data. It is a necessary component of modern software paradigms such as microservices systems.

API security is the process of protecting APIs against attacks. APIs are becoming a popular target for attackers due to their widespread use and access to necessary program functionality and data.

API security is a critical component of modern web application security. APIs are prone to problems such as faulty authentication and authorization, a lack of rate restrictions, and code injection. APIs must be tested on a regular basis in order to detect vulnerabilities and remedy them using security best practices. This article discusses several approaches and tools for API security testing, as well as a variety of recommended practices that can assist you in securing your APIs.

Why is API Security Important?

API security is critical because if an attacker gains access to and control over an API, they may manipulate the services to which your APIs link and potentially steal the data that an API may be utilizing. APIs are the software industry's infrastructure; thus, having access to them implies having access to whatever data APIs are pumping from product to product or service to service. Security is a crucial aspect that should not be overlooked since APIs expose sensitive data and business logic to third-party apps and services. REST API security is critical for maintaining the confidentiality, integrity, and availability of data sent between systems.

A hacked API can expose you to a variety of security risks, including data theft, illegal access, and denial-of-service attacks. Hackers can get access to sensitive information, modify data, or insert malicious code onto the target system by exploiting vulnerabilities in inadequately protected APIs.

As a result, significant security measures are required to safeguard REST APIs from prospective attackers. Authentication, authorization, encryption, and input validation are security measures that can assist in decreasing the risks of API attacks while also ensuring secure data transit between systems.

How to Secure REST API

There are many techniques to secure your REST API. Some of them are discussed below.


It is the most basic of all procedures, and it is also the most often employed. For simple authentication, you just utilize login and password fields. You enter your username and password into the form and send it to the server, and the program recognizes you as a user and provides you access to the system unless an error occurs.

The biggest issue with this security method is that credentials are sent directly from client to server. Credentials are only Base64 encoded in transit and are not encrypted or hashed in any manner. Any sniffer might read the transmitted packages across the network in this manner. As a result, HTTPS is frequently suggested over or combined with Basic Authentication, which completely encrypts the connection with the web server. The best thing about this is that no one can tell from the outside that Basic Auth is taking place.

DIGEST Authentication

This authentication technique encrypts the password given by the user, called the password hash, before delivering it to the server using hashing algorithms. This clearly makes it far more secure than the traditional authentication approach, in which the user's password travels in plain text and may be readily read by anybody intercepting it.

Client CERT Authentication

This is a technique that uses certificates to establish a trust relationship between the server and the client. When a client seeks to access a protected resource using this method, it gives the certificate to the server instead of giving a login or password. In addition to a unique private-public key pair, the certificate provides user information for authentication, including security credentials. The server then checks the CA to see if the user is legitimate. It must also confirm that the user has access to the resource.


Open Authorization 2.0 (OAuth 2.0) is a mechanism that allows a website to access resources kept by other web apps on behalf of a user. OAuth 2.0 is a protocol for authorization, not authentication. As a result, it is primarily intended to enable access to a collection of resources, such as distant APIs or user data.

Access Tokens are used in OAuth 2.0. An Access Token is a piece of data that identifies the ability of an end-user to access resources.OAuth 2.0 does not define an Access Token format.

Common API Security Threats

The following are some common API security threats that you may run into:

  • Man-in-the-Middle Attack: A man-in-the-middle (MITM) attack occurs when an attacker intercepts a query or response between an end user and an API. They may steal the transmission's contents, for example, credentials or information, and can also change the response.
  • Injections: APIs with flaws in security and compliance are also vulnerable to code injections, which occur when an attacker delivers a script to the server of an application via an API request. This script is designed to disclose or remove data, plant fake information, and/or affect the internals of the program.
  • DDoS attacks: The most straightforward API attack is a basic denial-of-service attack designed to take an API offline by overwhelming the underlying servers. . Botnets may execute massively parallelized assaults on an API, and scripts make this process simple to automate. Rate limitation is a useful protection, but it may be circumvented by rotating source IP addresses or faking origin headers.

API Security Best Practices

The following are some best practices that can improve your REST API security.

  1. Use API Gateways: API Gateways assist businesses in routing API queries, organizing API answers, and managing service level agreements (SLAs). API gateways facilitate the usage of APIs, but they are also vital for security since they provide encryption and access control. Even better if you’re using Kubernetes-native solutions (such as Edge Stack).
  2. Use authentication: A critical API security component verifies that the correct program makes the correct request. HTTP basic authentication, OAuth authentication, and API key authentication are three of the most prevalent ways of API authentication. It is best to authenticate APIs at all levels and use caution while storing API keys.
  3. Use Transport Layer Services (TLS): Transport Layer Security (TLS) should be used by all online APIs. TLS encrypts your communications while they are in transit, protecting the information your API sends (and the information users give to your API). A third party might intercept and access sensitive information in transit, such as API credentials and private data, if TLS is not used. That compromises whatever authentication mechanisms you implement.
  4. Conduct frequent security testing and look for API flaws: Even if other API security best practices are in place, organizations must undertake frequent security testing and API vulnerability scanning. Even organizations that have successfully moved left would benefit from regular checks and assessments.
  5. Validate API data: Validating API data ensures that incoming API data matches your expectations. Validation is the process through which your system confirms that incoming data is of the appropriate kind and structure. Sanitization is the process through which your system removes potentially harmful characters from incoming data.
  6. API services should be updated: Keeping everything up to date is another essential cybersecurity strategy that pertains to API security. For API security, this involves making sure your APIs and your API documentation are up to date.
  7. Use a Web Application Firewall (WAF): A web application firewall (WAF), (such as the one we use in at Ambassador Labs) is software that stands between your API and the internet, preventing harmful data from reaching your server. It's an excellent approach to defend against DDoS assaults and other harmful activity.

Keep Your API Security Top of Mind

Developers must guarantee that their APIs are not only functional but also secure and that attackers are not able to compromise the API. Security should be considered throughout the API development lifecycle, and developers should ensure that key concepts like authorization and authentication are understood. API micro-firewalls and API Gateways, should be used by both developers and security teams to offer extra levels of protection to APIs.

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