Black, Grey and White Box Testing

Black, Grey and White Box Testing

Posted by Peter Bassill on 17/11/2021

Penetration Testing Methodologies

What are black, grey, and white box test?

The pentesting industry loves colour. There are different roles within pentesting assignments; Red Team, Blue Team, Purple Team and others. The colours do not stop there. Different types of a penetration test are termed by colour too. We often see white, black, and grey-box pentesting being used. Have you ever wondered what they mean?

This blog article will describe the three types of pentesting, how to choose the right type for a given assignment, and if your dream job is in our industry, how to become a pentester yourself.

What is black, grey and white-box testing?

Pentesting engagements are typically classified based on the level of knowledge and access initially granted to the pentester. The colours become lighter with more information. Starting from the darkest edge, we have black-box testing. Black-box pentesting is where the tester has minimal knowledge of the target system. Opposite this is white-box testing, where the tester has high levels of documentation, information and access.

Black Box Penetration Testing

In Black Box penetration tests, the penetration tester have the same role as the infamous "hacker". The tester has no internal knowledge of the target system. The only information available is information that is in the public domain. A black-box penetration test is used to identify vulnerabilities in a system that are exploitable from outside the network.

Black-box penetration testing relies a lot on the tester's skills to dynamically analyse running programs and systems within the target network. For success in a black-box penetration test, the tester must be familiar with automated scanning tools and methodologies for manual penetration testing. The tester must be a master of documentation, creating their map of target systems and networks based on their observations. We use Xmind to help our testers create a dynamic map of our thought processes and actions and our findings during a test.

The black-box penetration test is one of the quickest to run since the duration of the assignment largely depends on the tester's ability. However, a black-box penetration test often needs more days than initially envisioned, as testers will often uncover more "interesting" items during the pentest. The significant downside to this approach is if testers cannot breach the perimeter, internal vulnerabilities go unnoticed.

Grey-box testing

Following the black box is grey-box testing. Suppose a black-box tester is examining a system from an outsider's perspective. In the case of a grey-box pentest, the penetration tester has an ordinary user's access and knowledge levels, potentially with elevated privileges on a system. Grey-box pentesters typically know a network's internals, potentially including access to design and architecture documentation and an account internal to the network.

The purpose of grey-box pentesting is to provide a more focused and efficient assessment of systems, applications and networks. By using the available documentation for the business, the pentesters can focus their assessment efforts on the assets with the most significant risk. Having an internal account allows security testing inside the hardened perimeter and simulates an attacker with longer-term access to the network.

White-box testing

White-box testing goes by several different names. It can be called clear-box, open-box, auxiliary and logic-driven testing. In a white box penetration test, the penetration testers have full access to source code, architecture documentation and more. It is reasonable to consider a white-box test as simulating a malicious or rogue IT team member. The main challenge with white-box testing is the amount of data gathered. It takes time to work through the massive amount of data available to identify potential points of weakness. A white-box penetration test is one of the most time-consuming types of penetration testing. It is also one of the most comprehensive forms of penetration testing, providing the most expansive coverage to identify security weaknesses and vulnerabilities.

Unlike black-box and grey-box testing, the testers can perform static code analysis during a white-box penetration test. That means familiarity with source code analysers, debuggers and similar tools necessary for this type of testing. Dynamic analysis tools and techniques are crucial as static analysis tools and techniques can miss vulnerabilities introduced by the misconfiguration of target systems.

White-box penetration testing provides a comprehensive internal and external vulnerabilities assessment, making it the best choice for calculation testing. The close relationship between white-box pentesters and IT and development teams provides a high level of system knowledge. Still, it may affect tester's behaviours since they operate based on knowledge not available to hackers.

Advantages and disadvantages of different testing methodologies

If all pentesting methodologies worked equally well, there would only be one. The different testing types have their advantages and disadvantages. The tradeoffs between black-box, grey-box and white-box penetration testing are cost, the accuracy of the test and speed, and efficiency and coverage.

Accuracy and Purpose

Penetration testing is used to identify and patch the vulnerabilities, weaknesses and misconfigurations that an attacker might exploit. For simulating a true attack, a black-box pentest is best as most attackers do not know the internal workings of their target network before launching their attack. However, the average attacker will spend considerable more time on thier attack than is permitted on a penetration test. Other methodologies were designed to decrease engagement time by increasing the level of information provided to the tester.

The opposite to black-box testing is white-box testing, where testers have complete information about their targets. However, this increased level of knowledge will cause testers to act differently from black-box hackers, making it more a technical audit like the IT Health Check.

Grey-box testing exists between white and black testing. Providing the penetation tester with limited information about the testing scope, the grey-box test simulates a level of knowledge a hacker would aquire during a long-term attacker that might carry out.

Speed versus Coverage

All three methodologies make tradeoffs between speed, efficiency and coverage, which is why we offer penetration testing to any of these three. Black box penetration testing will always be the fastest but the limited information available increases the liklihood that vulnerabilities, weaknesses and misconfigurations might be overlooked and decreases the accuracy of the test.

Grey-box testing makes a slight tradeoff in speed compared to black-box testing in exchange for increased efficiency and coverage. Access to design documentation allows testers to focus their efforts better and internal access to the network increases the range of the analysis.

White box penetration testing is the single most comprehensive form of pentesting, and needs significantly longer to complete. The high level of information provided prior to the test increases the chances that the majority of vulnerabilities will be identified and can be successfully remediated.

You want to be a pen tester?

An effective and valuable penetration tester requires a combination of knowledge, documentation discipline and an excellent pentesting toolkit.

Training and certification
GIAC, The Global Information Assurance Certification, has both a Pentester (GPEN) and Exploit Researcher and Advanced Penetration Tester (GXPN) certification as well as many others. GIAC is the top tier of training, and while it carries a very hefty price tag, it is undoubtedly well worth it. Offensive Security is the body behind the Offensive Security Certified Professional (OSCP) certification, which is excellent value for money but takes longer to complete and can be a more demanding skill mountain to climb.

eveloping a penetration testing tool kit
Building your penetration testing tool kit is an ongoing process. It never stops. Penetration testers who are just starting their careers often use existing toolsets created by other penetration testers and hackers, such as Kali and similar. As you gain experience, it's not uncommon to start to build up a collection of self-written scripts and tools you create to make your life simpler. These tools are invaluable. They can automate common or complicated processes that you see often in engagements. Dont get bogged down by which langauge to learn. Simple tools only require nothing more than a scripting language like Bash, Python, Powershell or Ruby.

Remember, there is no one right tool, but many tools that might be right.


Black, grey and white-box penetration tests have different approaches, and each simulates how a hacker would attack a network and identify and patch the vulnerabilities discovered. Most penetration tests would be black-box in an ideal world since they closely resemble how a hacker approaches a network. However, time and budgetary constraints and the desire to detect and remediate vulnerabilities inside the perimeter have led to the creation of grey-box and white-box penetration testing methodologies.

While black-box and grey-box use primarily dynamic analysis methodologies, white-box penetration testers must also be proficient with static analysis techniques. Becoming a talented penetration tester requires practice and familiarity with various tools, techniques and targets.

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