White Box Penetration Testing: A Brief Guide

White Box Penetration Testing: An Introduction 

In this guide, we will discuss what white box penetration testing is, as well as discussing black box penetration testing, grey box penetration testing, and the various benefits associated with it. 

What is Penetration Testing? 

Defined simply, penetration is where an ethical hacker is given access to a network, system, mobile application or website. The aim of this test is to simulate a cyberattack, with the goal of discovering any weaknesses or vulnerabilities that the system might have. 

The test is therefore a method of hacking into a system before any cyber attackers or cyber criminals get the chance to do so. 

The name given to this ethical hacker is a “pentester”, short for penetration tester.

The Three Types of Penetration Tests 

As mentioned earlier, there are different types of these tests – gray, black and white. For the time being we will focus on the white, before briefly explaining what the black and grey types of pen tests are, so that you can understand the key differences between them. 

White Box Test 

You may be familiar with the term open box testing, which is an alternative name for white box penetration testing. 

The pentester is given full and complete access to the system. 

This includes a total understanding of the source code, infrastructure, network architecture, login details and more. 

As stated above, this is so that they can simulate a cyberattack on the system, so they have all the resources to access all different areas of the system itself. 

Later in the article, we will discuss how this works. 

Grey Box Test 

The next step down (or up, depending on which way you look at it) is grey box testing. This is where the pentester is given some access to the system they are hacking, rather than

full access like in the white box test. 

This is a more realistic way of simulating a cyberattack and is typically seen as a halfway house between white box and black box testing. 

While the white box can define an organisation’s weaknesses and vulnerabilities, grey box exploits their weaknesses to insider threats, because they still need some level of access. This is useful if a cyberattack has happened because someone inside has access to credentials and giving them away. 

Black Box Test 

Black box and white box penetration testing could not be further from each other. As the name suggests, it is the complete opposite. And this is also true. 

Black box (also known as close box penetration testing) gives the pentester no login information, or system information, or any of the accesses that grey and white testing offers them. 

But why? 

The goal of a black box penetration test is to simulate the most realistic type of cyberattack. 

Typically, a cyberattack will come out of nowhere, with you having no knowledge that someone else may have your details – this is exactly the case with a black box test. 

Although it simulates the most realistic type of cyberattack, it can be very time-consuming – especially given the time that it takes the pentester to access the accounts or system in the first place. 

On top of this, the pentester may actually completely bypass or miss any vulnerabilities, depending on which way they decide to access (or hack into) the system. 

In the remainder of this article, we will focus on the white box methods – which we will discuss in greater detail below. 

White Box Testing: How It Works 

Before you get started, there are a range of different tools which can come in useful for white box testing. 

These are listed below. 

  • JUnit. A software testing framework which helps developers test their applications. It allows developers to write tests in Java and run them on the Java platform. 
  • NUnit. An open-source unit testing framework for the .NET framework and Mono. It has the same purpose as JUnit does for Java. 
  • John the Ripper. A password-cracking tool which can run on 15 different platforms. (No relation to Jack!) 
  • EclEmma. Short for Eclipse Emma. A Java code coverage tool for Eclipse.
  • Metasploit. A computer security project which provides information about security vulnerabilities. It aids in penetration testing and IDS signature development. 

Below we will outline the steps that you need to take to perform a white box penetration test. 

The Different Types of White Box Testing 

While they all aim to achieve the same result, you will still need to understand the different types of white box testing and what they mean. 

They are also typically undertaken at different times during the testing process.

Unit Testing 

This is done to confirm whether or not a certain type of code is running, in order to check its functionality. 

This is generally performed during the early steps of the process because unit testing helps to remove any simple errors. Therefore, this forms one of the basic steps of the performance. 

Static Analysis 

This is used for measuring the static sections of the code. 

Should there be any errors or defects of any kind, static analysis helps to sort it out. This is also usually undertaken during the first few steps of the process because it means that any errors are removed early on. 

Dynamic Analysis 

This step typically immediately succeeds static analysis. However, many developers think that static and dynamic analysis should be undertaken together. 

This is because with the aid of dynamic analysis, the source code is analysed, and then executed afterwards. 

The output (or final result) is also analysed, but this does not affect the process.

Statement Coverage 

Statement coverage is probably the most important step of the testing process. The advantages are obtained during the steps of execution. Statement coverage helps in analysing whether or not the functionalities are in working order.

The reason why this step is so fundamentally important and cannot be ignored is that every single function is executed, even if it is only once, so that you have a clear picture of where any loose ends might be. 

Branch Testing Coverage 

As the name suggests, the patterns branch out here. 

This is because the web and the software applications are not programmed in a continuous pattern. 

Instead, they are branched into different ways so that the process of segregation can be effectively undertaken. 

The main benefit of this is that branch covering helps to find results quickly – meaning less time (and money) is spent on the laborious parts of the process. 

In this process, the branches are verified like codes. Should there be any anomalies (or unnatural elements) in the application, they are easily found with the aid of this code. 

Security Testing 

This is one element of white box penetration testing which has to be absolutely perfect at all times. 

This is often the main reason white box testing is done in the first place, so security testing is rarely ignored. On the contrary, they are undertaken by almost every tester. 

Because the application has to be naturally protected automatically, it is required that there has to be a formulated process. 

Security testing is one of the elements which takes longer because there are a multitude of subsections involved in it. 

Should there ever be any unauthorised access, the security testing helps in rectifying this. Likewise, if there is the risk of any security breaches, the process prevents this, too. 

Mutation Testing 

Mutation testing is almost always the last step when it comes to white box penetration testing. 

What it is is essentially a re-checking technique. The reason for this is so that it can find any bugs and defects. 

The primary benefit of mutation testing is that it helps in obtaining more information about the strategy.

In turn, this makes the system stronger at regular intervals of time. 

How To Perform the Test 

Now you know the different types of testing, as well as why these are important, now it is the time to discuss how to actually perform the test. 

There are a few steps to take into account, so these will be outlined below, in chronological order. 

Step 1: Select the Areas You Want to Test 

Making sure you know which areas you want to test for is paramount before undertaking white box testing. 

One important bit of advice is to narrow down the core parts of the system. The narrower the test is, the better it is likely to be. 

The reason behind this is because the way the test is set out is that it runs every potential scenario which can run code alongside code. 

If you have a particularly large area, it will be more difficult to identify all of the problems. On the contrary, with a smaller area, you are making it easier to focus on numerous problems which may arise, just in that small area. 

Of course, if you wanted to cover a large area, this is still possible, it is just much more difficult as well as time-consuming. This means that it is also much more costly because you are using up an internal member of staff’s time to do so, or paying extra for an external pentester to do this additional work for you. 

Step 2: Identification 

Firstly, you will want to outline all of the potential code lines. 

Following this, you will then need to identify all possible codes in either the aspect or in the functionality of the system that you want to perform the test on. 

Finally, write the output of each code in the flowchart. 

The reason for this is because it will help you to keep track of everything, keeping the process streamlined, organised and straightforward, while at the same time, identifying the possible code and any permutations. 

Step 3: Write Test Cases 

It is absolutely essential that test cases are written for every step.

The reason behind this is because this is where arguably the most important work lies. 

Every test case should address what could possibly go wrong, what might end up going wrong, and where certain vulnerabilities may lie. 

Step 4: Execute the Test 

You have finally reached the final part of the white box testing journey – you can execute the test after all of this preparation! 

You can put all of your plans into motion – this is the first part of executing the test. 

Next, you can start completing all of the actions that you have previously laid out in your plans – security testing, branch testing and so on. 

But whatever you do, never just stop after one test or the whole process is redundant. Make sure that you test, test, and test again until you have covered all of the systems which have been outlined above. 

Once you are confident and satisfied that there are no issues left which need to be solved, then you can end the test. 

Why White Box Testing? 

If you have read this far into the article and you are still unsatisfied, that’s understandable. In a moment, we will outline the numerous advantages and disadvantages which are typically associated with white box penetration testing, but for now, we will answer this pressing question. 

The reason you should consider white box penetration testing is because of its rigorous approach. 

Because of the range of different levels, it can be executed at – from unit level to integration level and even right up to system level – the working flow of the application is therefore identified with the assistance of white box testing. 

Advantages and Disadvantages of White Box Penetration Testing 

As with any system, there are a range of advantages and disadvantages associated with white box testing. Below we will discuss both so that you can come to your own conclusions on whether or not you think that white box testing is for you. 


  1. Time saving. Especially in comparison to black box testing, but even when compared to grey box testing, white box testing is by far and away the quickest method. This is because the pentester has already been given full and complete access to the application or system, so it saves the time it would manually take them to work out the login details. 

  2. Automation. As with many different types of technology in 2023, using AI (artificial intelligence) can greatly assist with white box testing. This also goes hand in hand with the time-saving element, given that the traditionally lengthy processes can be replaced with AI or machine learning. 

  3. Identify issues early. The process of white box testing can be performed early during the Software Development Learning Cycle (SDLC). In fact, it can even be performed before the user interface comes about. This means that the developer can fix any bugs extremely early in the process, rather than discovering them just as a new product is about to be launched. Similarly, it also means that any security issues can be identified and rectified during these early stages of the development process. 

  4. Modifiable. Because of how early any issues can be identified, this means that any apps can be secured while it is still in development, making it easier for any other developers or any issues that may arise further down the line. 

  5. Transparency. Because of the nature of the white box testing, great clarity can be achieved through testing this way – the internal system is able to be tested because of the clear nature of the test. 


  1. Missing functionalities. Because only the code is tested, certain functionalities could be missed out completely. 

  2. Difficult process. Many developers will stay away from white box penetration testing as it is a tedious, laborious process. 

  3. Time consuming. Depending on which way you look at it, white box testing can either be time-saving or time-consuming. For argument’s sake, it can be time-consuming because any of the codes may have to be redesigned. This also means that the codes have to be redesigned alongside any of the test cases, which also need to be rewritten. 

  4. Expensive. Finding a tester who will willingly undertake white box testing is one thing, but this also comes with a price – and it is an expensive one at that! This is because it requires the use of highly skilled pen testers who have the ability to understand the software’s internal logic. Naturally, these types of testers are expensive to hire. 

  5. Overly-technical. When it comes to important stakeholders in your company or business, white box testing can sometimes be too technical for them to understand the benefits of it. This means that it may be unable to go ahead, even after meticulous planning. 


While there are clearly some setbacks when it comes to white box testing, there are numerous advantages which make this a process worth undertaking. 

On top of that, white box testing should be undertaken to identify any potential issues or security breaches early in the process of app and software development.