What is API security testing?

An API is a set of rules and protocols that enables different software systems to interact with each other and exchange data. APIs are the driving force behind our modern digital infrastructure, allowing systems to communicate programmatically with each other and share features. 

APIs are ubiquitous, critically working underneath most of the activities of our daily digital lives. They also often have access to sensitive information. Because of this, APIs have become prime targets for malicious actors. Most notably was an attack on Uber’s API in 2016 that exposed the personal information of 600,000 drivers and 57 million users. Uber was fined $148 million, demonstrating the potential damage of API vulnerabilities and the importance of API security testing.

API security testing helps teams address vulnerabilities early and often throughout the API development process. In this article, we’ll explore common API vulnerabilities and effective testing methods you can use throughout the API life cycle.

Common API vulnerabilities

The primary role of an API is to enable data exchange. But if it isn’t secured properly, an exploited API can allow attackers access to sensitive data or disrupt functionality. The Open Web Application Security Project (OWASP) publishes an annual list of the top 10 API security risks. This OWASP Top 10 is a helpful resource for DevSecOps teams needing to secure and test their APIs. In this section, we’ll highlight some of the most commonly seen vulnerabilities from that list.

Broken Object Level Authorization

Broken object level authorization (BOLA) is a vulnerability that occurs when an API fails to verify whether a user is authorized to access certain data objects or perform specific actions. Attackers exploit this vulnerability by manipulating requests or object IDs to access other users’ data. This vulnerability usually arises due to improper implementation of access controls. 

For example, an employee might be able to manipulate request parameters or object IDs to access restricted information (such as the salary data of other employees), expose sensitive data, or access other confidential files.

Broken Authentication

Broken authentication occurs when an API fails to verify the identity of users correctly, making it a prime target for attackers seeking access to user data. These vulnerabilities often arise from poor implementation of authentication protocols and weak password policies.

For example, consider a banking application that allows users to log in with weak passwords. There is no added security, such as a one-time password (OTP) or multi-factor authentication (MFA). This insecure implementation would be considered broken authentication, as attackers may guess weak passwords through brute-force attacks, gaining access to sensitive data.

Excessive Data Exposure

Excessive data exposure happens when an API responds with more data than is actually needed, relying on the client to hide it. This vulnerability is often a result of poor design and lack of data filtering. However, it can result in serious data breaches, fraud, and loss of user trust.

For instance, imagine an API that sends sensitive details like a credit card number alongside account data, relying on an application’s front-end HTML or CSS for concealment. In this scenario, attackers can inspect the source code or make direct API requests to access the sensitive data.

Security Misconfiguration

Security misconfigurations occur when an API is not set up correctly or is deployed with insecure default settings. This can leave the API vulnerable to attacks or expose sensitive data inadvertently. These misconfigurations are typically caused by a lack of security awareness during deployment or a failure to apply the necessary security patches.

One example of a security misconfiguration is leaving debug mode enabled in a production environment. This may expose sensitive information — such as API keys and third-party credentials — for attackers to exploit.

Lack of Rate Limiting

Rate limiting enforces a limit on the number of requests a user or system can make to certain endpoints of an API within a window of time. It is a security technique used to prevent denial-of-service (DoS) attacks and thwart brute-force attempts to guess passwords.

Attackers can take advantage of a lack of rate limiting by forcing their way into the API through numerous API calls, overwhelming the system and causing service downtime.

This vulnerability occurs when developers overlook or ignore the need for rate limiting. This failure to account for rate limiting affects business performance, as service downtime can impact business profitability and customer experience.

API security testing: A life cycle approach

API security testing is an ongoing security process spanning the entire life cycle of the API. Continuous testing throughout the development and operational phases helps DevSecOps teams catch and address vulnerabilities early to minimize the opportunities for attacks in production.

API security testing focuses on systematically evaluating, testing, and implementing security measures. It is implemented in the following stages:

Discovery and inventory

The discovery and inventory stage involves cataloging all APIs. This includes internal APIs, third-party APIs, and shadow APIs. From a security standpoint, the functionality of an API dictates how sensitive the API is, providing insight into its susceptibility and how to address those vulnerabilities.

Shift left testing

Shift left testing is a popular approach to development, referring to the practice of initiating testing earlier in the development process. A shift left methodology in API security testing involves testing your API for security vulnerabilities within continuous integration/continuous delivery (CI/CD) pipelines. This approach helps catch and fix vulnerabilities early, reducing the likelihood of larger issues later.

Runtime protection

API security extends beyond development to include real-time protection during runtime. This involves continuously monitoring APIs to identify suspicious activity that could indicate or lead to attacks. AI and machine learning tools for API testing can be used to analyze behavior patterns, helping to detect and resolve cyberattacks in real time.

Contextual threat detection

To further strengthen API security, it’s important to analyze and monitor usage patterns of APIs to identify low and slow attacks that might evade other detection methods. By monitoring API traffic over time, a security team can identify gradual changes that may indicate a security threat. This contextual threat detection reveals vulnerabilities not typically caught in standard testing, strengthening the overall security strategy.

Automated threat mitigation

Using automated tools to find and fix API vulnerabilities enables security teams to more quickly detect and resolve security issues. By automating the threat mitigation process, security measures are consistently applied, strengthening your overall API protection against current and future risks.

Test and secure your APIs with comprehensive solutions

APIs offer enormous benefits. They contribute to faster and more responsive services, but they’re also valuable targets for attackers. Though identifying API vulnerabilities is a good first step, truly securing your APIs against rapidly evolving threats demands a robust and comprehensive API security strategy.

The partnership between CrowdStrike and Salt Security is designed to protect your APIs at every stage of the API security testing life cycle. This API protection integration helps you automatically discover and inventory all your APIs — including hidden ones — and catch vulnerabilities earlier through shift left testing. With real-time monitoring and protection, you can secure your APIs continuously from development to deployment. 

Find out how CrowdStrike and Salt Security can help protect your APIs today.