What is Penetration Testing? (AKA Pen Testing)

Quick Definition: A penetration test, also known as a pen test, is an authorized cyberattack on a network or a system designed to test its capabilities and find vulnerabilities. 

Imagine you're a bank manager who wants to see how secure your vault is. You might hire a team to try to break in and see how well it holds up. Can they get past the guards? Are locks easy to pick, or are they able to find a way to evade your security systems? How much they are able to access—and how they get there—will provide you with information about vulnerabilities you need to improve. 

The same is true in network security. How well someone can access your system can tell you a lot about its security. In this post, we'll explore what penetration testing is, the different types, and how they help assess network security.

What is Penetration Testing?

A penetration test, also known as a pen test, is a simulated cyberattack on a network or system. These authorized cyberattacks are designed to evaluate the network or system's security.

Usually, a company solicits and hires a team to attack itself, hoping they'll uncover weaknesses or vulnerabilities. How much the target knows about the penetration test before and during the simulated cyberattack is different for every penetration test, which is often referred to as black box testing, white box testing, or gray box testing. We'll explore those in more detail in a later section. 

In a typical pen test, ethical hackers (also known as penetration testers) use various techniques to probe a system’s defenses. This might involve trying to bypass security controls, exploit known software flaws, or even trick users into revealing sensitive information through phishing. By mimicking the tactics of real attackers, pen testers can highlight issues like outdated software, weak passwords, or misconfigured settings, all of which could lead to a security breach if not addressed.

What is Black Box Testing in Penetration Testing?

Black box testing is a term used in any software testing — not exclusively penetration testing. The name comes from the idea that a user's inputs go into a "black box," and the software's outputs come out: the user doesn't know what happens inside the black box to produce those outputs. 

In a broad sense, usually in software testing, black box testing is a method of testing for functionality without any knowledge of what the internal code looks like. In penetration testing, black box testing is searching for vulnerabilities without any credentials or intimate knowledge of the system's or network's setup.

What is White Box Testing in Penetration Testing?

White box testing is also a term used in software testing. In white box testing, the internal structure and design of the code are being tested. The name comes from the idea that it's the exact opposite of black box testing: the detailed workings of the code, programming, network connections, and system details are not only known but manipulated during the test. 

In a broad sense, white box testing is a method of testing for internal details about the code. In penetration testing, white box testing is searching for vulnerabilities with full access to all components of the target network, system, or application's source code.

What is Gray Box Testing in Penetration Testing?

Last but not least, there is gray box testing. Gray box testing falls somewhere between white box testing and black box testing. For example, during a gray box test, the tester may have been given a username and password, or they may have been provided with a general overview of how the system works, but they may not have been given the details.

It's not unheard of for gray box testers to be told what the application they're testing against does and what it interacts with but not be given the source code for the application. In the case of network penetration testing, maybe they're given a network schema but not detailed data about the devices on the network.

Gray box testing is the broadest category of penetration test because it refers to a pen test in which the team has some, but not all, information about the target. The amount of information they have usually reflects what the security team is trying to uncover about the target.

An Overview of Black vs Gray vs White Box Testing [VIDEO]

In this video, Keith Barker covers black, gray, and white box testing as it relates to vulnerability scanning and penetration testing. He clarifies the difference between box testing and hat testing, meaning how black box penetration testing is an entirely different concept from black hat activity.

What is the Difference Between Black Box Testing and White Box Testing?

Black box testing is a penetration test in which the pen testing team has no prior knowledge of the details of the network, systems, or servers that are currently in the system. They're basically starting from scratch.

On the other side of the scale is white box testing. With white box testing, the person doing the testing has full knowledge and access. They have a username and password, are familiar with the source code, and likely have a working copy.

During white box testing, the penetration testing team is fully familiar with the system. They have all the details regarding the system, the server, or the application that they're going to test against. So with White Box Testing, with full knowledge beforehand, the tests are going to be more specific in nature.

For example, if we look at every line of the source code and know that certain parts of the code are solid, we won't waste our time testing against those. However, if we do look at the source code with white box testing and see a gaping hole wide enough to drive a truck through, that's absolutely part of the code that we're going to test during our white box test.

When to Perform Black, Gray, or White Box Testing

Organizations looking to ensure their security practices are up to snuff often choose to conduct penetration tests. These tests can reveal security holes before an attacker can find them and provide lots of metrics and data that security teams can use to mitigate future vulnerabilities.

When you're testing a system—and that could be against a network or a specific application running on a server—different categories of testing can be done. Like with broader software testing, the various categories of penetration testing reveal other things about the network being tested. As we've discussed, those categories are black box, white box, and gray box tests.

Each test reveals different things about a network or system, and knowing what you're trying to uncover is essential before selecting which box test you'll undertake. Are you interested in the functional aspects and requirements of your security procedures, or are you looking to validate the internal structure of your underlying security-based code?

Are you looking for the equivalent of a security guard patrolling the building's doors and windows, or are you looking for a full-blown and thorough investigation, equivalent to doing background checks on each employee and studying building blueprints for vulnerable areas? The former is a black box test, while the latter is closer to white box testing.

Is Pen Testing Illegal?

No, penetration testing is not illegal. Remember, the tests are performed by the company itself. While some sections of the team may not be aware it's a pen test, someone (and usually most of the leadership team) is aware. 

Are White Box Testing and White Hat Hacking the Same Thing?

No, white box testing is not the same as white hat hacking. Just like black box testing is different from black hat hacking, white box testing is also distinct from its hacking equivalent. That said, there's more overlap between them than with black hat hacking and black box testing.

White hat hacking refers to an authorized individual attempting to uncover security vulnerabilities. It's not the same as white box testing, which involves testing for vulnerabilities with full knowledge of the target network.

But it is a square-rectangle comparison. A white hat hacker uses tools to investigate and discover a target network and then test the network in an authorized fashion. A white box test involves full access and knowledge of a system before it begins, so a white hat hacker could be operating in a white box testing environment. Still, it doesn't necessarily have to be.

What would someone with full knowledge of the system and who is fully authorized to use hacking tools against the network be called? Maybe a White Hat, White Box Hacker Tester? Or a White-White Hat-Box Hacker-Tester? That much we'll leave to you.

Wrapping Up

Penetration testing is an essential service tool for any organization that is serious about security. Whether it's a black, white, or gray box, each type of pen test serves a unique purpose. It helps to identify different vulnerabilities based on how much information is provided to the testers. By simulating real-world attacks, companies can uncover weaknesses before malicious hackers do, ensuring their networks and systems are better protected.

Want to learn more about pen testing or become a pen tester yourself? The International Information System Security Certification Consortium offers the CISSP certification. CompTIA Security+ is another great certification option, and we offer over 29 hours of training and 277 videos to help you prepare. 

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