Test Methods: White-, Black- and Grey-Box - Which one is right for me?

As digitalization continues to advance, IT security is moving ever higher on the corporate agenda. One of the most important testing methods is the penetration test. It reveals how secure your system is and identifies gaps that you should address.

Detect Security Vulnerabilities in Time With Penetration Testing

Regardless of your industry, the progress of digitalization is clearly evident. Even small and medium-sized businesses are affected. Processes are being digitized, systems interconnected, and data from critical business applications increasingly migrated to the cloud.
This shift brings greater flexibility but also raises the risk of encountering cybercriminals. That makes testing methods like penetration testing an essential component of your IT security strategy. After all, cyberattacks pose challenges that should not be underestimated.
Regular security assessments help you keep your existing IT infrastructure secure. You reduce the attack surface available to criminals and eliminate potential vulnerabilities before they cause problems.
Regardless of your company's size, you should perform penetration tests on a regular basis. This ensures that your sensitive data remains protected in the long term.

Cyberattack and Security Analysis

Critical business applications that you use online or on mobile devices pose an increased security risk. That does not mean you have to forgo them -- but it is important to take appropriate precautions.
Through targeted security analysis, cyberattacks can be intercepted or reduced to a minimum. Does your company rely on smart supply chains or store large volumes of personal data? Such data represents a valuable asset that must be protected with the right IT security testing methods.
The key challenge is identifying vulnerabilities and security gaps. Only when you know where they exist can you take targeted countermeasures.

What Is a Penetration Test?

A penetration test is a testing method that allows you to evaluate the security of your IT systems. IT experts deliberately attempt to break into and manipulate your network or systems. The techniques they use closely mirror those employed by hackers or crackers. Because the experts operate in a similar manner to real attackers, they can pinpoint where the system is vulnerable. Regular security audits using these methods make it possible to realistically assess your threat exposure.
Throughout the penetration test, the testers document every action taken. Afterward, you receive a detailed report outlining the identified vulnerabilities along with concrete remediation recommendations. The risks are also classified, so you know which gaps to address first.
While the test reveals where action is needed, remediation of the vulnerabilities is not part of its scope.

Different Penetration Test Methods

Depending on the system you want to test, different methods come into play.
To simulate a classic cyberattack, an external penetration test is performed. The expert attempts to penetrate your internal network via the internet. The focus is on your firewall and systems located in the demilitarized zone (DMZ). If the attempt succeeds, the tester can then access your data.
In an internal test, the company network serves as the starting point. The expert already has access to the internal network. This test reveals what damage can occur if an attacker gains access to an employee's device. An important consideration: an attack from the inside causes significantly more damage in a shorter time than an external attack.
Beyond these, numerous other types fall under the umbrella of penetration testing. Which variant is appropriate and how it is conducted depends on additional factors -- such as the specific test method and the level of knowledge the experts have about your system beforehand.

Testing Methods: What Are White Box, Black Box and Grey Box?

In penetration testing, methods are often differentiated by color. For example, blue, red, and purple teams each handle specific PenTest tasks.
Colors are also used to classify tests by knowledge level and access granted: White Box, Black Box, and Grey Box. Each method serves a specific purpose and is suited to a different scenario. The classification depends on how much information you share with the pentester about your system in advance. In black-box testing, the tester has only minimal knowledge of your IT system, whereas in white-box testing, extensive information is available upfront.
If you are commissioning a security audit for the first time, a black-box test is typically the preferred choice. If you have your IT security tested annually, however, most organizations opt for white-box methods.

White Box Penetration Test

In a white-box test, the pentester already has full knowledge of your organization's IT infrastructure. This includes your servers, operating systems, applications, and services. The tester also knows which ports are open -- or at least should be.
With this information, the test is particularly effective. The reason is straightforward: the tester can begin evaluating the systems immediately and perform a thorough target-versus-actual comparison.
This method is also known as Auxiliary or Logic Driven testing. It sits at the opposite end of the spectrum from a black-box test. Full access to architecture documentation and source code creates entirely different challenges: vast amounts of data must be analyzed and potential vulnerabilities systematically uncovered. This makes the penetration test particularly time-consuming.
The result is a comprehensive assessment of both external and internal vulnerabilities. If you want to perform an authorization test, the white-box penetration test ranks among the best methods for your security audit.

Black Box Penetration Test

In a black-box test, the tester has no knowledge of the IT infrastructure and must therefore proceed exactly like a real attacker. The advantage is that the pentester independently gains an overview of the infrastructure. This means the test primarily uncovers vulnerabilities that are externally visible and could be exploited by third parties.
Due to the limited knowledge involved, this method is the fastest to carry out. The exact duration depends on the tester's skill level. The downside, however, is that internal vulnerabilities remain undetected if the pentester fails to penetrate the perimeter.

Grey Box Penetration Test

The grey-box penetration test combines elements of white-box and black-box testing. The pentester has foundational knowledge of your IT infrastructure -- such as what the systems are used for and how they are generally structured.
The grey-box method is the most commonly used type of penetration test in practice. This is because certain IP ranges are defined in advance, and you can selectively exclude specific applications from the test scope.
A grey-box tester typically has the same level of knowledge and access as an employee. You may even grant elevated privileges. This enables the tester to evaluate your network security in a targeted manner and conduct independent analyses. An additional advantage is that the tester can focus directly on the systems that carry the highest risk.