Black-Box, Gray Box, and White-Box Penetration Testing: Importance and Uses

December 4, 2023
| David Tidmarsh
| Penetration Testing

Penetration testing is a cybersecurity best practice that involves working with an organization to probe its IT environment for vulnerabilities. By discovering these weaknesses in advance, penetration testers hope to resolve or mitigate them before they can be exploited during a real cyberattack.

Penetration testing is pivotal in helping organizations detect IT security vulnerabilities and harden their defenses against potential cyber threats. Understanding the differences between black box, grey box, and white box testing is essential for any would-be pen tester. So, what is black box, grey box, and white box testing in cybersecurity, and what are the use cases of each type?

What Are Black, Gray, and White-Box Testing?

Black-box, gray-box, and white-box testing can be distinguished as follows:

  • Black-box penetration testing (close-box penetration testing) is perhaps the most challenging and realistic form of penetration testing. As the name suggests, black-box penetration testing involves assessing the security of an IT environment or system without any prior knowledge of its inner workings.
  • White-box penetration testing (open-box penetration testing) is the opposite of black-box penetration testing. During a white-box test, pentesters have full knowledge of and visibility into the target IT environment.
  • Grey-box penetration testing sits somewhere between black-box and white-box testing. In a grey-box pentest, the testers may have limited or partial knowledge of the target of their attacks. Depending on the type of test, grey-box pentesters may know a little about the entire system or a lot about only part of the system.

Advantages and Disadvantages of These Testing Methodologies

Black-Box Testing: Pros and Cons

The benefits of black-box penetration testing are:

  • Greater realism: In most cases, the perpetrators of a cyberattack are external to an organization and have little to no insider knowledge about the target’s IT ecosystem. This makes black-box testing a more realistic assessment of the organization’s security posture.
  • Comprehensive evaluation: Black-box penetration testers often perform reconnaissance to comprehensively evaluate the target’s defenses. This can help widen the scope of the penetration test and identify weaknesses that may otherwise have gone undiscovered.

However, black-box penetration testing also comes with concerns and limitations:

  • Lack of internal visibility: Black-box testers face the initial challenge of breaching the target’s external defenses. If the IT environment’s perimeter is secure, testers will be unable to discover any vulnerabilities within internal services.
  • Difficulty replicating: Penetration testing can take many forms, from simple automated vulnerability scanning to highly complex attacks. Black-box testers may struggle to replicate advanced attack scenarios due to limited knowledge about the environment

White-Box Testing: Pros and Cons

The benefits of white-box penetration testing are:

  • Full knowledge of the system: White-box testers can perform a more comprehensive security assessment than black-box testers, who may still lack crucial information after launching the attack.
  • Static code analysis: White-box testers usually have access to programs’ source code and can perform static code analysis, unlike black-box testing (Dewhurst, 2023). This involves debugging software by scanning the code for vulnerabilities without running the application itself.
  • Insider threat scenarios: An insider threat is an individual internal to an organization who causes harm to that organization as a result of their privileged access to IT resources (CISA, 2023). White-box pentesters can more realistically simulate insider threat scenarios.

White-box penetration testing also comes with certain downsides, such as:

  • Too much information: White-box testers have access to massive amounts of data about an IT environment, which can itself be a disadvantage. Testers need to effectively sift through all this information and efficiently identify potential targets for attack, which means that white-box penetration testing can be more time-consuming.
  • Greater expertise: The comprehensive evaluation performed by white-box pentesters means that white-box teams need a wider range of IT expertise. White-box penetration tests may cover everything from network architecture to program source code, so testers must understand various security vulnerabilities.

Gray-Box Testing: Pros and Cons

The benefits of a gray-box pentest include:

  • Partial knowledge scenarios: Grey-box penetration testing can simulate advanced persistent threat (APT) scenarios in which the attacker is highly sophisticated and operates on a longer time scale (CISA, 2023). In these types of attacks, the threat actor has collected a good deal of information about the target system—similar to a gray-box testing scenario.
  • Striking the right balance: Grey-box penetration testing allows many organizations to strike the right balance between white-box and black-box testing. For example, a fully white-box test might not be feasible due to resource or time constraints, while a fully black-box test might yield incomplete results.

The main disadvantage of gray-box testing is that it can be too “middle-of-the-road” when compared with black-box or white-box testing. If organizations do not strike the right balance during gray-box testing, they may miss crucial insights that would have been found with a different technique.

Black-Box Vs. Gray-Box Vs. White-Box Pen Testing

Black-box, gray-box, and white-box pen testing differ in several ways, including:

  • Knowledge level: The further along the spectrum from black to white, the more information testers have about their target. Black-box testers are least informed, with no insider secrets, while white-box testers are most informed, with full visibility into the system.
  • Objectives: Black-box testers seek to simulate attacks from an external threat with only publicly available information. White-box testers seek to thoroughly evaluate a system’s cybersecurity using internal details and resources. Gray-box testers sit somewhere between these two extremes.
  • Use cases: Black-box testers represent the perspective of external hackers, and white-box testers represent insider threats. Gray-box testers can represent various types of scenarios based on the type of information they have access to.

How Is Black, Gray, and White Box Testing Performed?

The differences between performing black, gray, and white-box testing are as follows:

  • Black-box testing: In a close-box pentest, penetration testers need to collect information about the target over the course of the test. They are typically provided with only minimal information to start with, such as a web application URL or an IP address. Black-box penetration testers must then fill in the gaps in their knowledge, such as by creating diagrams of IT architecture or scanning for vulnerabilities.
  • White-box testing: Before the white-box test begins, pentesters are supplied with all the information they request about the organization’s IT ecosystem. This may include details about application source code, system configuration and design files, network users, and more.
  • Gray-box testing: Gray-box testers may start with limited information about the IT environment. For example, they may have a high-level sketch of the system architecture or access to a limited number of user accounts. However, they may need to collect more data to successfully infiltrate the target.

Once testers receive these preliminary details, all three penetration testing methods are highly similar. The main difference between performing black, gray, and white-box testing is that the “blacker” the box, the more information testers will need to collect themselves during the test.

Learn All 3 Pen Testing Strategies with C|PENT

Black box, grey box, and white box testing are all valuable forms of penetration testing, each with its own pros, cons, and use cases. Penetration testers need to be familiar with the importance and use cases of each type of test to execute them most efficiently, using the right tools for each one.

Understanding the difference between black box, grey box, and white box tests is just one of the many factors in penetration testing and ethical hacking scenarios. If you’re interested in becoming a penetration tester or ethical hacker, obtaining a certification that proves your knowledge of the field through real-world experience is an excellent idea.

EC-Council’s Certified Penetration Testing Professional (C|PENT) course is the most comprehensive penetration testing certification in the industry. Over the course of 14 theoretical and practical modules, C|PENT students learn to identify weaknesses in a range of IT environments, from networks and web applications to the cloud and Internet of Things (IoT) devices. In particular, C|PENT students learn about white-box, black-box, and grey-box penetration testing and the different tools and techniques used in each of them.


Dewhurst, R. (2023). Static Code Analysis. OWASP.

CISA. (2023). Defining Insider Threats.

CISA. (2023). Advanced Persistent Threats and Nation-State Actors.

About the Author
David Tidmarsh is a programmer and writer. He’s worked as a software developer at MIT, has a B.A. in history from Yale, and is currently a graduate student in computer science at UT Austin.

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