Companies have increased their reliance on APIs to boost their business models because they offer more integration, efficiency, and personalization. However, as organizations rapidly rise to adopt APIs, threat actors have started exploiting vulnerabilities within the system too.

To be precise, we can say that it is easy for hackers to exploit the API security vulnerabilities, resulting in data theft or a man-in-the-middle attack. A hacker might attack when APIs are sensitive, as APIs connect and process your valuable and confidential data amid the systems and applications. Thus, it would help if you made every effort to secure APIs.

API security testing is one proven method to ensure that the APIs are safe and free from vulnerabilities. So far, several practices are available that you can adopt to reduce the API security risks, for example, through data encryption, authorization, authentication, identifying the vulnerabilities, and more.

But, above all, API security testing is a great way to protect the integrity of both third-party and internal APIs. The security testing process ensures that the APIs are safe and without any API security vulnerabilities.

A vulnerable API can lead to security breaches and other cyberattacks, which we will explore below.

Why No One Should Neglect API Security Testing

An organization’s most valuable asset is its data. Any threat or risk to its data can pose a significant threat to the entire organization. With the advancement in technology, targeting APIs is the easiest way for attackers to gain access to your data.

According to The State of API Security, Q1 2021, 91% of organizations experienced an API security incident in 2021. Besides this, there are several other incidents of API data breaches too.

For example, security researcher Bob Diachenko recently discovered an API vulnerability in Facebook that resulted in a massive data breach. The data breach exposed more than 267 million Facebook IDs, user names, and phone numbers in a publicly accessible database.

Similarly, in December 2018, a Facebook photo API bug exposed private photos of up to 6.8 million users in a data breach. The API bug allowed third-party developers to access photos shared with the service, allowing the apps to keep content after the users ended their access or delete the data.

Neglecting API security testing can lead to massive data breaches. Therefore, your organization must have a plan that instructs the developers and others to practice API security testing. The testing process informs about API vulnerabilities and comes up with different aspects to prevent attackers from exploiting the vulnerabilities. Overlooking API security testing can cause:

• Customer data leaks
• Decreases the number of users
• Damages your online reputation

Given the numbers and types of security breaches, API security testing is vital to the application development process. So, you shouldn’t ignore it.

Methods for API Security Testing

Gartner predicted that by 2022, APIs will be the common attack vector for data breaches within any business organization. There’ve been incidents in the past that resulted because of unprotected APIs. It’s because most of the APIs were not tested for meeting the security criteria. It also means that the APIs you’re using might not be secure.

Considering the importance of API security testing, below, we’ve explained the best methods you can use to test your APIs.

Fuzzing Test

Fuzzing testing is one of the most simple methods used for detecting web API vulnerabilities. To put it simply, fuzzing means providing random data to the API till the point it spills something out. This data could be some error message, information, or anything else to signify random data processed by the API.

This testing method doesn’t involve any advanced tools and programs; that’s why it’s quite popular and widely used. You can execute this test by using command-line tools like curl.

You can use curl to send unexpected values to the API to see if it breaks or not. An imperfect coded application has a particular format so, this is an excellent way to find bugs within your application.

Test for Parameter Tampering

The parameters sent through an API request are vulnerable to tampering. An attacker could tamper with them to change the values of a product and buy it for free. Parameter tampering testing ensures that the threat actors do not modify the product value within the APIs.

You can perform the parameter tampering test in two different ways:

• Changing the query parameters in API requests: You can test different combinations of incorrect query parameters to see if the API returns with the proper error code.
• By changing input fields in a web form: Web apps use input fields that are often hidden, and one can only read them in the backend. So, don’t forget to test your app’s backend and see if it is validating the data within the hidden input files. You can do so by searching for the input elements, changing the values, and submitting the form. Make sure that you check all the variables and not only the hidden ones.

Test for Unhandled HTTP Methods

Web applications that communicate using APIs use various HTTP methods for storing, saving, or removing the data. If a server does not support an HTTP method, it should display an error. However, this is not always the case for vulnerable APIs.

To test such vulnerabilities, you need to make a HEAD request to your API endpoint that requires authentication.

Test for Authentication on All Endpoints

To check some other endpoint vulnerabilities, try to access the endpoints with invalid tokens or credentials. By doing so, you can ensure that the web service is responding correctly with the proper message and status code.

Test for Secure Code Reviews

Potential API vulnerabilities keep arising due to insecure code. It poses dreadful consequences and proves to be a significant challenge for cybersecurity professionals. Thus, by reviewing and testing the security code, one can detect the security issues within your app.

Without any doubt, this is one of the best methods for API security testing. It focuses on identifying vulnerabilities in the apps related to authentication, authorization, data validation, error handling, encryption, logging issues, and security configuration.

In the testing phase, the secure code of any app undergoes an auditing process to make sure that the business and security controls are in the right place. Remember, you can conduct this test both in automated and manual ways to ensure the security of the applications.

Three Ways That Can Breach API Security

Among the others, there are three ways that attackers can use to exploit API and gain access to your sensitive data. These include man-in-the-middle, parameter, and replay attacks.

1. Man-in-the-Middle Attacks

When the hacker stands between an API and an app or user, it results in Man-in-the-Middle attacks. The absence of SSL/TLS from an API often results in such attacks. The attackers intercept the traffic between the two entities and sometimes pretend to be one or the other.

2. Parameter Attacks

These attacks exploit the data sent to the API using the URL, parameter query, SQL injection, or HTTP header. SQL injection attacks are the most common parameter attack. Such attacks take place when the developer fails to sanitize the inputs. The attackers take advantage of such a moment and exploit the vulnerability. In SQL injection attacks, the hacker uses SQL code to direct the backend database to access sensitive information. The data might be related to private customer details, bank account details, or personal details.

3. Replay Attacks

In this method, the cyber-crooks first spy on secure network communication, intercept it, and then redirect the target to do what the attacker wants. Such attacks are most dangerous because the hacker can intercept without having the decryption keys. They only need to target an encrypted communication channel without having any access to decryption keys.

Parting Words

There are quite a few ways to improve your API security. Besides implementing API security best practices, you can also utilize API security testing methods. These API security testing methods can help you minimize the security risks and vulnerabilities that can negatively impact your business.

We recommend that you follow the testing methods mentioned above and enhance your API security levels.