What is API Security Testing?

April 4, 2024 | by Jeff Harrell

A stylized image of an arrow pointing up and to the right and bisecting several images suggesting development milestones.

In short, API security testing involves the systematic assessment of APIs to identify vulnerabilities, coding errors, and other weaknesses that could be exploited by malicious actors. Application Programming Interfaces, or APIs, provide much of the communication layer between applications that house an organization’s critical customer and company information, and API security testing is essential to ensuring the integrity and resilience of those applications. It is APIs’ extensive connectivity and access to critical systems that exposes them to a myriad of security risks, making them prime targets for attackers.

Why is API Security Testing Needed?

Web application-specific security tools are typically not designed for API security testing and are at best less effective at fully addressing API security. Web-oriented dynamic application security testing (DAST) tools lack the context needed to test APIs based on their designed function. Effective API security testing requires understanding the business logic of the API – what it was designed to do. Many of today’s API attacks are related to business logic abuse, such as account takeover (ATO), SIM fraud, or gift card abuse. The unique vulnerabilities and use cases for APIs vs. applications is the reason that the OWASP standards body maintains separate Top 10 lists for web applications and API security.

How API Security Testing Can Protect APIs

  • Protecting Sensitive Data – APIs often handle sensitive information such as user credentials, personal data, and financial details. API coding errors or misconfigurations could lead to unauthorized access, data breaches, or simply sensitive data leakage.
  • Preventing Malicious Attacks – In the past, attackers focused mainly on the applications, but now it’s common for attacks to include the APIs as well, or even bypass applications entirely to attack their underlying APIs. API security testing enables proactive identification and mitigation of potential attack vectors and reduces the risk of API attacks such as account takeover, broken authentication, and business logic abuse.
  • Maintaining Regulatory Compliance – Data protection regulations such as GDPR, CCPA, and HIPAA legally require organizations to ensure the security and privacy of user data. API security testing helps organizations demonstrate compliance with regulatory requirements by identifying and rectifying security gaps.
  • Preserving Brand Reputation – A security breach can result in financial losses and tarnish the reputation and perceived trustworthiness of the organization. API security testing is a proactive step towards safeguarding the organization’s brand reputation and maintaining customer trust.

Key Components of API Security Testing

API security testing during and after the development process is a vital component of the API protection lifecycle, necessary to protect company assets. Some key components of API security testing include:

  1. Authentication: Evaluating the effectiveness of authentication mechanisms in verifying the identity of API consumers and preventing attacks such as credential stuffing.
  2. Authorization: API-specific use cases like broken function level authorization (BFLA) and broken object property level authorization (BOPLA) have been called out in the OWASP API Security Top 10 and testing must ensure that only authorized users have access to specific API methods (e.g. GET, PUT, POST) or data objects (e.g. name, address, SSN). These are API-specific test cases that aren’t covered under web application testing, and as such require an API security testing-specific solution.
  3. Cross-account access: Vulnerabilities such as broken object level authorization (BOLA) and insecure direct object references (IDOR) are critical API-specific test cases.
  4. Encryption and data integrity: Assessing the adequacy of encryption protocols employed to safeguard data transmission and storage and ensure that data integrity and confidentiality are preserved.
  5. Rate limiting and throttling: Testing the implementation of rate limiting and throttling mechanisms to mitigate the risk of API abuse and denial-of-service (DoS) attacks with support for customizing these values as needed, such as between development and production environments.

A Necessary Component of the Development Process

Integrating API security testing early in the development lifecycle follows the “shift-left” approach, wherein security considerations are addressed from the initial stages of development. Identifying and remediating issues early in the development process is typically easier and less resource intensive than fixing security issues at later stages.

One of the perceived hurdles in agile and DevOps-focused environments is that security assessments hinder the pace of innovation. However, modern API security testing tools and methodologies that seamlessly integrate with development workflows enable continuous security testing without impeding development velocity.

What to Look for in an API Security Testing Solution

When choosing an API security testing solution, look for a few key capabilities:

  • Integration with pre-production environments – a solution that integrates with CI/CD pipeline environments such as GitHub, Gitlab, Azure DevOps, Bamboo, or Jenkins.
  • Broad API test coverage – the solution should support common test and vulnerability frameworks such as the OWASP API Security Top 10, include customizable tests, and help ensure your test cases reflect actual API usage.
  • Support for multiple API sources – the ability to generate test plans from various sources such Postman Collections or OpenAPI specs.
  • Integrations with existing toolsets – in addition to the CI/CD pipeline environments mentioned previously, the ability to integrate with SIEM, SOAR, and ITSM products can help enable multiple stakeholders in their preferred workflows.
  • Autonomous test creation – in some cases, API specifications may not be available, so a solution that is capable of generating specs automatically and without human involvement will eliminate a great deal of manual work.
  • API protection integration – while most people think of API testing as part of the development process, it’s important to think of it holistically – don’t just shift left, but shield right into production. The best API security testing solutions are part of a broader platform that can protect the entire API security lifecycle.

Part of the Cequence Unified API Protection Platform

Cequence offers an API security testing product as a module in API Sentinel that enables IT security and developers to thoroughly test their APIs to identify and remediate vulnerabilities and coding errors. API Security Testing is an integral component of the Cequence Unified API Protection platform that addresses every phase of the API protection lifecycle.

API security testing is not merely a checkbox in the development process; it is a fundamental necessity for safeguarding digital assets. Embracing a proactive approach towards API security testing and integrating it into the development lifecycle enables organizations to identify vulnerabilities before they’re exposed in production environments. To learn more or set up a private demo of Cequence’s API security testing capabilities, simply schedule a demo.

Jeff Harrell


Jeff Harrell

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