What Is a Gray Box?

What Is a Gray Box?

Let me explain what a gray box is in the context of software testing. Gray box refers to testing software where you have some limited knowledge of its internal workings. As an ethical hacking technique, it means you, as the hacker, use that limited information to identify the strengths and weaknesses of a target's security network.

Key Takeaways

You should know that gray box testing is a technique for discovering software bugs or finding exploits, where some limited knowledge about the underlying software is known in advance. This form of ethical hacking allows software developers to create fixes and patches to prevent malicious attackers from utilizing these exploits. Essentially, gray box testing is a blend of white box, which involves full knowledge, and black box, which involves no knowledge, methodologies.

Understanding Gray Boxes

Gray box is the hybrid of white box testing, where you examine the internal logic and structure of the software’s code, and black box testing, where you know nothing about the software’s code. To grasp gray box testing, you must first understand black box testing and white box testing.

Black Box and White Box Testing

Black box testing looks at nothing more than inputs by the user and what output the software produces given those inputs. You don't need any knowledge of programming language or other technical details for black box testing. It's a type of high-level testing used in system testing and acceptance testing. Software engineers require a software requirement specification (SRS) document to perform black box testing. This testing takes an end-user perspective where you, as the black box tester, do not know how the outputs are generated from the inputs.

White box testing requires in-depth knowledge of the techniques and platforms used to build software, including the relevant programming language. It's a type of low-level testing used in unit testing and integration testing. You need to understand the programming language used to create the application so you can examine its source code. White box testing’s primary purposes are to strengthen security, examine how inputs and outputs flow through the application, and improve design and usability. When you, as a white box tester, do not get the expected output from a given input, the result is considered a bug that needs to be fixed.

How Gray Box Testing Works

Gray box testing includes important components of both black and white box testing to get a better result than either could obtain alone. Both end users and developers perform gray box testing with limited, partial knowledge of an application’s source code. You can do gray box testing manually or automatically. It's more comprehensive and time-consuming than black box testing, but not as much as white box testing. Gray box testers require detailed design documents.

Gray box testing involves identifying inputs, outputs, major paths, and subfunctions. It then moves on to developing inputs and outputs for subfunctions, executing test cases for subfunctions, and verifying those results.

Gray Box Example

Consider this example: you, as a gray box tester, might check and fix the links on a website. If a link doesn't work, you change the HTML code to try to make the link work, then recheck the user interface to see if the link works. Another example is testing an online calculator. You would define inputs—mathematical formulas such as 1+1, 2*2, 5-4, and 15/3—then check to see that the calculator provides the correct outputs given those inputs. As the gray box tester, you have access to the calculator’s HTML code and can change it if any errors are identified.

Gray box testing looks at both the application’s user interface, or presentation layer, and its internal workings, or code. It is mainly used in integration testing and penetration testing but it is not suitable for algorithm testing. You generally use gray box testing to test an application’s user interface, security, or online functionality through techniques such as matrix testing, regression testing, orthogonal array testing, and pattern testing. Gray box testers are most likely to identify context-specific problems.

“Gray” refers to your partial ability to see the application’s internal workings. “White” refers to the ability to see through the software’s interface to its inner workings, and “black” refers to the inability to see the software’s internal workings. Gray box testing is sometimes called translucent testing, while white box testing is sometimes called clear testing and black box testing may also be called opaque testing.

What Are the Advantages of Gray Box Testing?

Because gray box testing is meant to be conducted from the perspective of a user or hacker, it may reveal important flaws in the software that wouldn't be obvious to a developer approaching the testing from a development perspective.

Who Performs Gray Box Testing?

Both developers and security testers can conduct gray box testing. White box testing is conducted by developers and testers who are very familiar with the code used to write the software. Black box testing is conducted by testers who don't need to know the software's code. Gray box testing is a hybrid of the two and can be conducted by experts who conduct both white box and black box testing.

How Is Gray Box Testing Used in Cybersecurity?

Gray box testing can be used to see what kind of access a user has when signing into a website or app, and therefore, how easy or difficult it might be for someone to hack into the site with similar credentials, or without any credentials.