API security testing tools

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Recently, APIs (Application Programming Interfaces) have become essential to modern cloud, desktop, mobile, and web applications. They are now heavily relying on APIs to perform multiple functionalities. This expands the application landscape and allows developers to create feature-rich applications with simple yet diversified UX/UI.

Since API offers developers a great deal to produce versatile software, it also makes it vulnerable to multiple types of cyber attacks and data breaches, just like any other software system.

To ensure that APIs manage communication securely, it is crucial to implement appropriate security controls for unauthorised access to data or sensitive assets, functionality disruption, or other incidents that could question the APIs’ security.

In this blog post, we will discuss API security testing tools that help secure API, but before we jump into it, let’s understand what API security testing is all about.

What is API?

APIs are a set of programming protocols that integrate different systems, applications, and software to communicate, such as allowing data sharing, performing actions, or other functionalities.

api security scanning

What is API security testing?

API security testing scans and accesses an application’s API to identify security vulnerabilities.

APIs often offer access to sensitive information applications’ critical functionalities, and they eventually become a prime target for cybercriminals.

API security testing is integral in determining vulnerabilities such as injection, broken access control, low rate limiting, etc.

It also assists in applying adequate security controls to minimise exposure through API endpoints. Many open-source and commercial tools are available for API security scanning and penetration testing.

Some of the key features of the comprehensive and popular tools for testing APIs will be discussed further in this article.

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Automated API security testing

Automated API security tests use specialised tools or brilliant scripts to scan API against known vulnerabilities and evaluate the overall API security posture. The computerised tests involve the creation of use cases and custom-made scenarios to launch attacks on API.

Multiple open-source and commercial automated API testing tools in the market determine different types of vulnerabilities, such as injection, rate limiting, broken access controls, IDORs, etc. Some of the API tools also assist in generating reports with the appropriate recommendations to mitigate identified issues.

Automated API scanning saves time and resources in testing and securing API endpoints and increases testing coverage to detect security issues more quickly and efficiently.

Another great benefit is that API security tools can be integrated into the continuous integration and continuous delivery (CI/CD) pipeline to automate the API tests of various platforms throughout the entire software development life cycle.

The CI/CD pipeline integrated tool ensures that the API is thoroughly checked at each development phase and that developers know the loopholes, eventually enabling the development teams to fix the API security issues at the early SDLC.

Why use the manual API testing method?

It is indeed super beneficial to have automated API testing tools in the bucket, but relying solely on automated tools can not guarantee the highest security. Automated tools are data-driven and only run tests for known vulnerabilities and pre-configured test cases, but manual API tests help go beyond known security flaws.

To maintain security, it is essential to use a manual approach, as tools cannot replace the human expertise and knowledge that enable security experts to detect threats and exploit vulnerabilities.

For example, a tool can identify SQL injection or broken access control flaws in mobile applications based on the responses. Still, there could be false positives, or testing tools may miss other critical security issues, allowing attackers to chain up other vulnerabilities and launch successful cyber attacks.

Automated tools often miss vulnerabilities arising from business logic flaws, insecure design and implementations because they are not smart enough to chain vulnerabilities. They can not understand the business requirements. Only the human mind can comprehend and exploit them.

Therefore, businesses and security teams need not solely rely on automated testing tools. Instead, we must use manual testing to verify the accuracy of automatic test results, which also assists in validating the functionality and meeting compliance requirements.

With this combined approach, organisations and security professionals can use automated and manual methods to improve security and protect inter-connected assets and cloud environments against emerging threats and attacks.

API security tools

Various commercial and open-source testing tools are available in the market. Some of them are purely automated, and some offer a combination of both automatic and manual strategies. A few simple and easy-to-use tools to test APIs are as follows.

api security tool


Postman is a widely used API platform for API building, integration, documentation, and security testing of REST (Representational State Transfer) APIs.

It is an open-source tool that offers an intuitive interface with predefined API governance and API security rules, which automatically test API definitions and requests. It highlights security alerts for requests that differ from the pre-configured security rules.

Postman also allows users to execute API requests and responses, perform security analysis by adding dynamic variables, generate tokens and set headers and authorisation.

It supports functional and logical testing, load testing, performance testing, and integration testing. Also, it facilitates users to test security scenarios such as fuzzing, injection attacks, broken access control, and rate limiting.

Last, this tool has integration capabilities that can be added to the CI/CD pipeline to accelerate the continuous testing and security implementation with the security policy.

It assists developers and security experts in API monitoring, streamlining the API building and testing to identify and mitigate security risks on the spot.

Lastly, Postman allows users to add custom scripts for API security testing and supports various authentication mechanisms like OAuth 1.0, OAuth 2.0, and Basic Auth.

Burp Suite

Burp Suite is among the most powerful and widely used testing tools for automated and manual RESTAPI security testing. It came with a free community and paid version with many features that help testers identify potential API security flaws in modern web apps and microservices.

The Burp scanner enables the tester to intercept and modify the requests and responses for different scenarios. Its advanced crawling algorithm helps discover attack surfaces without user intervention and can handle JS-based heavy web apps.

The scanner parses the API definitions written in JSON, which assists in identifying and testing API endpoints that are not even intended for the web browser.

Burp API tests offer customised scanning configurations and can scan against the list of multiple common vulnerabilities and specific classes of API vulnerabilities, such as Injections, XXE, and XXS.

In addition, various tools and features can automatically test for API endpoints, bombarding many requests with multiple or different payloads through OAST (out-of-band application security testing).


ZAP is an open-source, free tool for API testing that helps improve web service security. The ZAP API scan is a script in ZAP Docker images that performs API security testing according to the specifications of OpenAPI. It also supports SOAP (Simple Object Access Protocol) and GraphQL.

ZAP imports API specifications and allows the tester to create, schedule, and automate the customised vulnerability detection according to OWASP best practices. As maintained by OWASP’s volunteers, it helps identify issues and tests the entire API with the famous yet crucial OWASP top 10 vulnerabilities.

api security scanning

Lastly, it can easily be integrated with third-party tools, API applications, and platforms, raising alerts on the top vulnerabilities and any HTTP server error response codes and content types.

Apache JMeter

Apache JMeter is a Java-based open-source tool primarily used for load testing and performance testing, but its diversified features enable it to be used for security testing. It is a cross-platform testing tool that supports macOS, Linux, and Windows.

JMeter is a powerful tool that can boost manual testing if the tester understands security best practices well. It can identify errors and enhance the vulnerability detection processes if tested or simulated with different scenarios.

Examples of such scenarios include manipulating HTTP requests/responses, tampering with authentication methods, testing for CSRF, injections, parameter manipulation, authentication bypass, and invalid credentials testing.

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APIClarity is a comprehensive open-source cloud-native tool that helps developers and security professionals identify and mitigate API security risks with greater visibility. It captures and analyses API traffic using a Service Mesh framework. This tool primarily focuses on OpenAPI-based APIs and offers a variety of modules to determine different aspects of API security.

APIClarity uses two different approaches to ensure API security. The first approach captures API routes and traffic in a given environment and performs testing to detect potential vulnerabilities with identified APIs.

The second approach tests API endpoints to identify weaknesses in implementing such APIs.

Since not every application has an OpenAPI specification available, APIClarity dramatically helps in the automatic reconstruction of OpenAPI specification based on observed API traffic, which is among the main functions of this tool. This function empowers the user to review and approve the reconstructed specifications and helps them address and ensure API security.

Parting thoughts

With continuous technological advancement, APIs are the foundation of many applications. As the APIs are here to stay and continue to grow, the need to remain vigilant has become essential for businesses, security professionals, and developers.

API security testing tools play a significant role in quickly detecting the API vulnerabilities in the CI/CD pipeline and identifying potential security issues before threat actors can exploit them.

Having an API security testing tool improves the collaboration between the development and security teams and minimises the risks of security incidents while streamlining the whole process efficiently.

Get in touch with us to discuss your security concerns.

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