What's the difference between black box and white box pen testing?

Steve Sutcliffe
By Steve Sutcliffe
To answer that question, we probably better start with an even simpler one; what is pen testing, or to give it it’s proper title, penetration testing?
What's the difference between black box and white box pen testing?
Well as the name does suggest it’s to do with testing things like your computer systems,  IT and network infrastructure to try and highlight any vulnerabilities which cyber attackers could exploit, before they can actually be exploited. The reason for doing penetration testing is to discover security weaknesses.

Typically, a penetration test requires three processes to be completed in order for it to be a successful test. The first process is research. This involves gathering information about the target of the test. The second process is actually conducting the test itself by identifying possible entry points for cyber attackers or actively attempting to break into the system or network. This attempt can be virtual or actual. The final process is reporting back the findings of the first two processes to the client so they can put the necessary security measures in place, to secure any vulnerabilities identified. All makes sense so far, right?

Back to our original question, what’s the difference between black box and white box pen testing?
Black box testing, is the software method of penetration testing. It’s used to test the software without the tester knowing the details of the code or program’s internal structure. The aim of this type of testing, is to gain an external perspective of the target being tested. It’s typically carried out by testers.

White box testing on the other hand, is the same method however, the internal structure of the code or software is known to the tester and the tester is typically a software developer. This type of testing provides an internal perspective of the target being tested and it requires internal knowledge of the test subject as well as programming skills.

There are advantages and disadvantages to both methods, so understanding these is key for deciding which type of testing is best for you.

Black box testing is highly efficient for large segments of code and code access is not generally required. That external perspective it provides also means that it separates the user’s and the developer’s perspectives. On the down side, it does only test a fraction of all the possible testing scenarios and it is blind coverage because the tester has limited knowledge about the test target.

White box testing is great for finding errors and problems in the test target, including hidden errors. It can also help with optimising the code of the test target. On the other hand, though, it does require a high level of internal knowledge about the test subject as well as sufficient code access. It also cannot identify missing or unimplemented features.

As a general rule of thumb, if you are looking to test functionality or external access to a system or network then black box testing is a good choice. If you want to test the structure of a system or network and investigate internal access, then white box testing is the best fit.

If you need to gain a better understanding of the potential vulnerabilities in your networks and infrastructure, get in touch with our experts today and we’ll be happy to help.

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Meet the MD: James Baird

Meet the MD: James Baird

"James Baird has been inspired by the integrity his grandad and father displayed, as he has navigated his career through being an electrician, starting his first business in electrical services and his current business, Dynamic Networks Group."