What do you know about API pentesting? Here at Sekurno, we are well-versed in the subject and would like to share our profound knowledge with you. If you are a beginner, this material introduces the perfect way to start your journey into the pentesting world. If you're a seasoned pro with years of experience in different cybersecurity companies, this post will help you recall some important nuances and peruse the common things from a new perspective.
The following article explains what API pentesting is and why it’s worth your attention if you own an application, website, online platform, or any project that somehow relies on APIs. Our vision of penetration testing goes far beyond the default cyberattack simulation backed by a few supplementary techniques. We consider API pentesting a more complex process that involves various new contexts and methodologies, offering additional value beyond its typical implementation.
To illustrate the complexity of API penetration testing, the article focuses on pentesting goals and approaches to achieving them. We compare whitebox, greybox, and blackbox techniques to show that there is no good or bad approach to penetration testing. You only need to use them properly on your way to clearly defined objectives.
Table of Contents
What Is API Penetration Testing?
You might be wondering, what exactly is API pentesting? To fully understand this concept, we need to break it down by first defining what an API is and then explaining what penetration testing entails. By understanding these two components individually, we can then piece together what API pentesting involves and why it's important.
Tireless Data Courier of Every System
While most of us know that API stands for Application Programming Interface, not everyone is familiar with the fact that it is a computing interface whose primary goal is to enable communication (you got it right — data exchanges) between two points. To achieve this objective, API defines methods and data formats suitable for requesting and exchanging information. As a result, different architecture components, such as mobile apps, web apps, etc., can work together seamlessly. But what if a threat actor tries to break the normal order of things within the system, exploiting API’s weaknesses?
Since APIs often handle sensitive data necessary for inter-application communication, they become the attacker’s number one target. Their exposure and critical nature attract hackers, and if you don’t minimize the risks, the wrong people get access to and in some cases even control over your system.
API vulnerabilities may become security breaches, and believe us, it is not something that you would enjoy. Therefore, it is essential to take robust security measures, including API penetration testing.
A Preemptive Strike on Security Loopholes
Consider pentesting a reverse preemptive strike that, instead of a threat actor, targets your system. It’s a simulated attack, a code review, or a combination of methods that aims to find security vulnerabilities in your application that malicious players could potentially exploit. But you won't let them do that. Since the bad actors are still unaware of the problem, you'll address it before they can reach out and harm your business!
Penetration testing works well because it is all about proactive security, meaning that you uncover potential flaws and address vulnerabilities preemptively before somebody exploits them. With numerous methods up the sleeve, it helps ensure compliance, reduce risks, or test the system’s security against simulated attacks. We will focus on these three aspects of pentesting below.
Customer trust, no matter whether you operate in the B2B or B2C segment, is an even more important asset you get by keeping your system safe, client’s data secure, and customer experiences flawless. According to Ping Identity, a data breach could be devastating for a business, as 81% of respondents would stop engaging with a brand online after such an incident.
A Check-up That Should Never Be Missed
As you might have guessed, API pentesting is penetration testing specifically focused on APIs. It uses the general methodology for detecting vulnerabilities and applies it to application programming interfaces.
API penetration testing is a cybersecurity practice that involves multiple techniques, from simulated cyber attacks on APIs to manual code reviews, to unveil any weaknesses in the API’s design, implementation, and configuration.
The arsenal of an API pentester is extensive. It encompasses a broad palette of diverse techniques, including but not limited to manual testing, automated scans, threat modeling, code reviews, etc. But which one works best? It's important to describe the goals of pentesting and the various approaches available before we can provide the answer.
Three Goals of API Pentesting
Companies conduct API pentesting for several key reasons, each tied to specific goals aimed at enhancing the security and integrity of their systems. These goals include:
Compliance: Many industries are governed by strict regulations and standards that mandate regular security testing to protect sensitive data. For example, healthcare organizations must comply with HIPAA, financial institutions with PCI-DSS, and companies operating in the EU with GDPR. In terms of cybersecurity compliance, pentesting helps ensure that legal requirements are met so that businesses avoid hefty fines and maintain their reputations by demonstrating a commitment to data security.
Risk Reduction: API pentesting can help companies identify and remediate vulnerabilities that could be exploited by malicious actors. This proactive approach minimizes the risk of data breaches, financial loss, and operational disruptions. A clear understanding of a security posture can help businesses prioritize and allocate resources to bolster defenses of the most critical places, ultimately reducing the overall risk to the organization.
Attack Simulation: API penetration testing can also be used to simulate real-world attack scenarios and evaluate the effectiveness of existing security measures. This hands-on approach allows companies to see how their systems would fare against various types of attacks, from common exploits to sophisticated threats. This realistic assessment helps understand potential attack vectors and the impact of security breaches, enabling more informed decision-making in security investments and strategies. Hence, businesses can improve their incident response strategies and fortify their defenses against future attacks.
Companies can tailor their security testing to meet specific objectives by selecting the right pentesting approach. But what are the different approaches available for API pentesting?
Different Approaches to API Penetration Testing
Depending on the access level, application testing can be implemented using one of these three approaches:
Blackbox Testing: In blackbox API penetration testing, the tester has no prior knowledge of the internal workings of the system. This approach simulates an external attack, where the tester attempts to identify and exploit vulnerabilities using only publicly available information and the API’s exposed endpoints. It focuses on how the API behaves under different inputs and scenarios without insight into the underlying code or architecture.
Greybox Testing: Greybox API pentesting involves a partial knowledge of the system when the tester has limited access to internal information, such as documentation, internal code snippets, or basic system architecture. This approach aims to combine the features of both blackbox and whitebox testing by simulating an attack with some insider knowledge.
Whitebox Testing: In whitebox API penetration testing, the tester has full access to the system’s internal workings, including source code, architecture diagrams, and other detailed documentation. This comprehensive visibility allows the tester to perform a thorough examination, identifying and addressing security issues that might not be apparent in blackbox or greybox testing. It provides the most in-depth analysis, covering both code-level and operational vulnerabilities.
At first glance, giving testers more access to a system would make API penetration testing more effective. Hence, whitebox testing, which offers the most detailed visibility, should be capable of uncovering issues that graybox and blackbox testing could miss. Let’s take a closer look to see if that assumption holds true.
What’s Better For API Pentesting: Blackbox vs. Greybox vs. Whitebox?
The following diagram compares whitebox, greybox, and blackbox approaches from the engagement scope and access level perspective:
While blackbox API pentesting is associated with simulated attacks created with minimum knowledge about the system in order to replicate real-world hacker assault, the whitebox approach leverages a more in-depth access level resulting in code reviews and other similar techniques. Does it mean you should choose only whitebox API penetration testing over blackbox or use both?
Everything depends on your goals. For instance, you want to reduce risks. Let’s compare whitebox and black-box.
Risk Detection Rate Speaks For Itself
According to the Web Application Security Consortium, the probability of detecting vulnerabilities of different risk levels varies between blackbox and whitebox testing as follows:
Whitebox testing shows superior results in all three categories: urgent, critical, and high risks. For urgent risks, it performs 2.5 times better, discovering 50% of vulnerabilities compared to only 20% with blackbox testing.
Whitebox testing is also more effective for critical issues, uncovering 92% of weaknesses and potential threats, while blackbox testing reveals 75%.
When it comes to high-risk vulnerabilities, the difference between whitebox and blackbox testing is smaller: 62% versus 59% detected risks, respectively. Nevertheless, whitebox testing still leads.
The Sekurno team once worked with a client who initially didn't want to conduct a whitebox pentest for security reasons. Our specialists performed a graybox test and identified only medium-level threats. Later, the client reached out again, and we convinced them to conduct a whitebox pentest, which then identified critical issues that the previous greybox testing could not detect.
This case clearly shows the importance of using the right methods to achieve your goals. Choosing the wrong approach won't yield the same results as techniques designed for the area you're targeting. While whitebox API pentesting is best for risk reduction and compliance, there are directions where blackbox is king of the hill.
What Blackbox Testing Excels At
The primary goal of blackbox API pentesting is to serve as an additional layer of risk mitigation. It complements other security measures by evaluating the effectiveness of existing security controls. These controls may include internal security code reviews, the implementation of a Secure Software Development Life Cycle (S-SDLC), and whitebox penetration testing performed by third-party vendors.
Blackbox API penetration testing allows for an independent, external assessment, objectively validating how well these security practices hold up against real-world threats. By testing APIs from an external perspective, blackbox testing can help identify vulnerabilities that might have been overlooked in internal reviews or during the integration of security processes. This holistic approach ensures that any gaps in existing defenses are exposed, further reducing the risk of exploitation and strengthening the overall security posture.
While blackbox testing provides a valuable external perspective in assessing API security, it's important to acknowledge the limitations outlined by industry standards like OWASP. According to the OWASP Application Security Verification Standard (ASVS), blackbox testing, despite being in use for over 30 years, has repeatedly demonstrated its inability to catch critical security vulnerabilities that have led to major data breaches. This history underscores the need for a broader and more integrated approach to security assurance.
OWASP advocates for replacing traditional blackbox testing with more comprehensive methods, such as hybrid penetration testing that combines both blackbox and whitebox techniques. In this approach, source code is directly analyzed alongside external probing, allowing testers to dig deeper into the system's inner workings. This type of hybrid test ensures a more thorough evaluation by identifying vulnerabilities that would otherwise remain hidden from the external view in a pure blackbox scenario.
Comprehensive Approach Makes A Difference
To ensure API pentesting detects all possible vulnerabilities, it is extremely important to evaluate the scope of work, conduct threat modeling, set the right goals, and carefully plan future testing routines. It will help you build a comprehensive approach to pentesting. And it’s what we do at Sekurno. Our team combines the following common methods to get the best results in finding security issues:
Static Application Security Testing (SAST) or Source Code Scanning: We use automated tools to review the source code and identify vulnerabilities, which is the whitebox approach.
Dynamic Application Security Testing (DAST) or Automated Penetration Testing: Our team employs automated pentesting tools to scan web applications through the front end, simulating attacks in a black/greybox environment.
Manual Penetration Testing: Manual API pentesting is more complex than automated testing. It involves specific tools and the expertise of our security specialists to perform more intricate tests. Manual pentesting can be performed as either whitebox, greybox, or blackbox testing.
Secure Code Review: Many of our security engineers are former developers, making us highly skilled at code reviews. This whitebox method involves reading parts of the system’s source code to detect potential vulnerabilities.
No single method can identify all security problems. It’s the number one thing that you should remember when talking to blackbox advocates. However, combining them works wonders. A comprehensive approach to API pentesting significantly reduces the risk of unknown issues.
According to OWASP, manual code reviews are more efficient in detecting general security vulnerabilities, privacy issues, and business logic bugs. Automated scans perform better than other methods regarding various compliance issues, such as HIPAA or PCI. And manual pentests are best for detecting availability issues.
Blackbox vs. Greybox vs. Whitebox Compared Against API Pentesting Goals
The following table illustrates how effectively blackbox, greybox, and whitebox methods align with various API pentesting goals:
Compliance | Risk Reduction | Attack Simulation | |
Whitebox | Covers all compliance requirements of standards and regulations including specific requirements of large customers (in some cases, enterprise clients may require whitebox over graybox and blackbox). | The most effective approach for identifying vulnerabilities, significantly reducing risk with full system access. | Due to its nature - mostly code review - it is not focused on external attack simulation. |
Greybox | Both are good to cover all standards and regulations but may not be enough for the specific requirements of enterprise clients. | Less effective than whitebox due to smaller coverage. More effective than blackbox because it can help reduce risks associated with internal threat. | Effective at simulating an attack with partial insider knowledge. |
Blackbox | Ineffective approach due to the nature of blackbox API pentesting itself. Inefficient time usage: Issues that could be quickly identified by reviewing the code often take much longer to discover, with the added risk of missing critical problems. Lack of system knowledge: Insufficient understanding of the system and processes prevents effective risk reduction. | A primary approach for simulating external attacks by testing how well security processes perform. |
Conclusion
API pentesting is essential for fortifying one of the system’s most vulnerable places — its application programming interface. Interoperability and data exchange hardly rely on APIs. Systems and their components interact with one another, no matter whether it is an e-commerce website, ERP module, SaaS platform, or any internet-driven service or architecture component. Even the smallest flaw in API security may ruin the entire ecosystem of interconnected elements.
In these conditions, API penetration testing becomes the organization’s crucial element in terms of cybersecurity strategy, counteracting real-world threats. It helps proactively identify and mitigate security risks, thereby safeguarding sensitive data and maintaining the trust of users, clients, and stakeholders.
Thanks to a wide range of blackbox, greybox, and whitebox techniques, API pentesting can help companies achieve some important security goals: risk reduction, cybersecurity compliance, and attack simulation.
Contact us for more information on the API pentesting services Sekurno provides. Follow the link below if you also think that "average security" is not enough!
API Pentest FAQ
What is API pentesting?
API pentesting is a cybersecurity technique that involves simulated attacks on the API, code reviews, and other methods to unveil any weaknesses in its design, implementation, and configuration.
What are the prerequisites for API Pentesting?
Before running any actual penetration tests against APIs, it is necessary to identify the specific APIs and endpoints that need to be tested. Next, understand their functionality and data flows. Establish the goals and objectives of the penetration test with this information in mind. These prerequisites will help you enhance your API pentest’s effectiveness and results.
What are the 3 types of testing in API?
Depending on the access level, testing in API can be divided into the following three types:
Blackbox testing: In blackbox pentesting, the tester has no prior knowledge of the internal workings of the system, simulating an external attacker's perspective.
Greybox testing: Greybox API pentesting involves partial knowledge of the system, combining aspects of both blackbox and whitebox testing.
Whitebox testing: In whitebox API penetration testing, the tester has full access to the internal workings of the system, including source code and architecture, providing a comprehensive assessment and audit.
What is the methodology of API penetration testing?
The API pentest methodology is a system of methods and principles for conducting cybersecurity audits that usually includes such different approaches, as simulated cyberattacks, source code scanning, automated penetration testing, manual penetration testing, and source code reviews. It is also important to include threat modeling in the methodology of API penetration testing to optimize processes and get better results.
