White Box Penetration Testing: How It Works

A white box penetration test is a simulated cyberattack, in which the penetration tester is given full access to, and knowledge of, the system being tested. With a full view of the system in question, the pen tester seeks out and attempts to exploit security vulnerabilities, so that the organization being tested can shore up its defenses following the test.

Because white box penetration testing offers an inside view of the system, the tester can examine points that may get missed during other types of penetration testing, such as issues with the logic flow of an application. These pen tests can be very comprehensive, with an especially sharp focus on internal assets.

White Box vs Black Box Penetration Testing

In black box penetration testing, on the other hand, the pen tester is given little to no information about the system. They start with as much knowledge as an actual hacker would, and must break in on their own, just like an actual hacker would.

Advantages of White Box Pen Testing

Because white box pen testers start with a full view of the system in question, white box testing is much more comprehensive than black box testing. White box testers can examine every aspect of a system in detail, without having to break in first via a difficult process of trial-and-error.

This level of knowledge means white box pen testing is generally more efficient. It isn’t always the faster method, however, since the testers start with more information to sift through. The greater the scope of the pen test, the more time and money it will take.

Because white box penetration testers have an inside view, they can place a greater focus on assessing internal vulnerabilities within a system. They start with access to source code, for instance, which means they can readily discover application logic flow issues that a black box tester might never encounter.

Drawbacks of White Box Pen Testing

White box penetration testing offers a less realistic simulation of a real-world attack than black box penetration testing does. Just like a real-world hacker, the black box pen tester starts with no information. They have to do their own reconnaissance and find their own way in.

For this reason, black box pen testing is often better for assessing perimeter security. A black box tester is going to spend more time and effort breaking into a system, using techniques such as phishing attacks that a white box tester wouldn’t need to deploy to get into the system. So while white box testing offers a more comprehensive look inside the system, black box testing offers a sharper analysis of what it takes to breach the perimeter.

White box pen testing can also be time-consuming. It offers a much more comprehensive analysis than black box testing, and it can certainly be more efficient at assessing security vulnerabilities inside a system. But the larger the system – and the scope of the penetration test – the more time and money will be required to complete it.

White Box vs Gray Box Pen Testing

As the name suggests, gray box penetration testing offers a functional middle ground between white box and black box pen testing. Gray box penetration testers typically start with limited information about the target system, and may have basic login credentials.

White box pen testers approach their assessments from a developer standpoint, analyzing systems in-depth to find vulnerabilities. Gray box testers mimic an insider threat, working to elevate the lower-level credentials they’re given to break into more sensitive areas.

White Box Pen Testing Stages

1. Scoping the Test

Before the pen testers can begin their simulated attacks, they must first get together with the company being tested and define the scope of the test. Both parties will get clear on what will be tested, when the test will take place, and how the tests will be conducted.

Because pen tests simulate real attacks, they have the potential to disrupt operations. By setting clear boundaries, both sides can minimize these disruptions. If an application is being tested, for instance, the testers might agree to conduct the test in a staging environment that replicates the application environment without affecting actual operations.

Once both parties have signed a contract defining the scope of the test, the testers can proceed to vet the system.

2. Identifying Vulnerabilities

Now the pen testers will examine the system closely in their search for vulnerabilities. They might start by running automated vulnerability scans – with full access provided in a white box pen test, these scans can be very useful, especially when it comes to checking for known vulnerabilities. Most white box pen testers will go further, examining an application’s code in detail via techniques such as path coverage and statement coverage.

As the pen testers work, they’ll compile their vulnerabilities into a list and draw up an attack plan for each item. The vital difference between vulnerability scanning and pen testing is that pen testers actually attempt to exploit the vulnerabilities they uncover, in a simulated attack on the network.

3. Exploitation

Now the pen testers will execute their attacks, manually verifying if the vulnerabilities they uncovered in the previous step can be exploited. This rules out any false positives a scan might have identified.

Even more importantly, any successful attacks can reveal new attack vectors. As the pen testers will work, they’ll pivot their attacks in light of new information, escalating their efforts with each attempt.

4. The Pen Test Report

Once they’ve finished their assessment, the pen testers will document what they found in a report. For the company being tested, the most important section will be the “findings,” which details every vulnerability the testers uncovered, what simulated attacks were run against each vulnerability, and the results of these attacks. Usually the testers will include a risk assessment score, so that the company being tested can easily prioritize the highest-risk issues first.

White Box Pen Testing Techniques

Statement Coverage

In statement coverage, the testers execute every single line of code in an application to see how each line functions. They might identify unnecessary lines, missing lines, and lines performing differently than intended.

Decision Coverage

Decision coverage, also known as branch coverage, examines the branching decisions within an application. Any given application is full of branching if-then clauses; this method tests every possible outcome of every possible decision point, searching for vulnerabilities.

Path Coverage

Path coverage is a methodical approach to closely examining each line of code in an application. Testers first map every path someone could take through an application, and then work through each path, one step at a time, in their search for vulnerabilities.

White Box Pen Testing Tools

Commonly used white box pen testing tools include the following:

  • CPPUnit
  • EclEmma
  • Efix
  • John the Ripper
  • HTMLUnit
  • JUnit
  • Metasploit
  • Nmap
  • NUnit
  • PyTest
  • Wireshark

For more information, see our complete guide to penetration testing.

About the Author

Find Michael on LinkedIn

Michael X. Heiligenstein

Michael X. Heiligenstein is the founder and editor-in-chief of the Firewall Times. He has six years of experience in online publishing and marketing. Before founding the Firewall Times, he was Vice President of SEO at Fit Small Business, a website devoted to helping small business owners. He graduated from the University of Virginia with a degree in English and History.