Black box penetration testing: definition, benefits, and techniques

The pillar of successful business is a high-quality product. In software development, this means a reliable solution that meets all requirements and operates well. To meet these goals, it is necessary to perform quality assurance at every stage of development. An integral part of this process is penetration testing (pen testing), also known as ethical hacking, which evaluates the security of a system.

In pen testing, there are three fundamental methods that look at the software testing process from different perspectives: white box, gray box, and black box. In this article, we provide a detailed overview of black box pen testing, including the benefits, challenges, techniques, and steps of this approach.

What is black box penetration testing?

The concept of a black box is an object that produces valuable information without disclosing any data about its internal workings. In penetration testing, black box means examining software with an unknown internal structure while working with the external interfaces of the system. Simply put, a QA engineer does not have access to the source code and checks the system from the user interface.

In the black box penetration testing methodology, QA engineers act as hackers with no inside knowledge of the target system providing the most realistic scenario of how a criminal can attack valuable information.

List of main features for black box penetration testing

Types of penetration testing: black box, white box, and gray box

All three types of pen testing have their own advantages in terms of the amount of information accessible to the tester.

White box

White box (also known as glass box, clear box, transparent box, and structural testing) implies testing of the software’s internal structure. The core difference between black box and white box penetration testing is access to the code—with the white box strategy, the QA expert has full knowledge of all elements of the system.

The focus is on verifying the input and output data flow, improving the design and usability, and enhancing security. To identify potential points of weakness, QA engineers sift through a large amount of data available, which makes this type of pen testing the most time-consuming. Furthermore, although white box pen testing provides a holistic assessment of both internal and external vulnerabilities, the high level of system knowledge may negatively affect testers’ behavior as they operate using information beyond the reach of hackers.

Gray box

This is a combination of white box and black box. Gray box testing requires incomplete knowledge of the internal processes. In other words, the code is known or used only partially. Having access to the internal structure and algorithms of the software, testers can write more effective test cases while the testing itself is performed from the user’s perspective.

Comparison table: black box vs white box vs grey box penetration testing

Benefits of black box pen testing

In addition to the “hacker’s mind”, black box pen testing offers the following advantages:

• It helps find errors that cannot be detected with the white box approach. For example, a developer missed a feature while working on the project. With the white box approach, testers will not find the error since the code is right and the software runs well. Meanwhile, the black box methodology detects the noncompliance with the specification.
• Test cases can be compiled immediately after the specification is in place. This significantly reduces testing time. Once the software is ready for QA assurance, test cases have already been developed and the testing can start immediately.
• Black box testing does not require programming knowledge. Since testers do not deal with the code, they do not have to know how the software has been implemented.
• The testing is conducted from the user’s perspective. Being the end consumers of almost every software, users are always right.
• Black box testing offers an unbiased view on the system. Usually, to test software with the black box method, third-party specialists are engaged.

Types of tests performed using the black box approach

Black box can be performed to test various aspects of a system or application, including:

Key types of tests in black box penetration testing

Functional testing. Experts check whether all features behave as declared in the requirements.

Integration testing. Testers check whether all components of the system work correctly as a whole. Regression testing. Specialists ensure that the new code does not lead to errors in the previous functionality.

Stress testing. QA engineers deliberately overload the program to evaluate the system performance under extreme conditions.

Security testing. Our black-box security testing experts test the software to evaluate security and identify any vulnerabilities that could be exploited by an attacker.

Compatibility testing. Testers check if the software or system is compatible with different operating systems, browsers, and devices.

Usability testing. QA specialists test the product from the standpoint of ease of use.

Beta testing. Testers evaluate a nearly finished product in the user’s shoes.

Acceptance testing. Checked by experts, the product is sent to the client, who verifies whether or not the software meets the requirements.

Testing techniques used in the Black box penetration approach

To detect all errors in a program, it is necessary to test all possible data sets. To do this, the black box strategy employs different techniques.

Equivalence Class Partitioning (ECP)

The essence of this method is to split the input data into groups and test only one sample from each. For example, if the site registration is available to individuals over 18, QA specialists can test only one date of birth in the “under 18” group and one date in the “over 18” group to see if the restriction works.

Boundary Value Analysis (BVA)

The technique is very close to the ECP method. BVA involves evaluating the ends or boundaries of input values. For example, a field accepts only numbers from 0 to 9. The testers can use the numbers -1, 5, and 10 to ensure that the input data is checked correctly.

Decision Table Testing (DTT)

This technique is used to visualize multiple combinations of inputs. In the table, testers insert the variables and the outcomes. Such a method allows QA engineers to summarize all the results of a situation in a convenient and сoncise way.

Example testing a decision table in a black box pen test

Error Guessing (EG)

As the name implies, this method consists of guessing the most frequent bugs. This technique is based on the tester’s proficiency, and therefore, requires extensive experience in the domain. EG does not follow any specific rules and can be used for checking common errors, such as dividing by zero, entering spaces in text fields, pressing the submit button without entering input values, and others.

Black box penetration testing steps

7 Stages of pen testing

Knowing the basics of the black box pen testing, the next step to uncover is how to perform it. To successfully carry out black box testing, do as follows:

• Examine the requirements since this is the main source of the expected results. To do this, a properly documented specification must be in place.
• Set valid/invalid inputs and the desired outputs to verify that the system detects them properly.
• Design test cases with various scenarios using the above-mentioned techniques.
• Execute the test cases to verify the actual results with the expected ones.
• Address the failed test cases to the development team so that they fix the bugs.
• Retest the software to ensure the bugs are not recurring.
• Perform the regression testing to verify that a code change does not impact the existing functionality.
• Report test results to provide valuable insight into the overall state of the product.

To automate the process by helping testers generate test cases, there are various software tools. Among them, the most popular are Selenium, Appium, Ranorex, UFT, AutoHotkey, Microsoft Coded UI, OWASP ZAP, Squish GUI Test Automation, and SilkTest.

The best test case management tools in software testing

Limitations of black box testing

The use of this methodology cannot solve all problems. Due to the lack of all-encompassing information about the software tested, the drawbacks are the uncertainty that the whole system has been examined and that security is strong. Black box testing cannot guarantee that all bugs are fixed as the practice implies examining a limited number of cases.

In addition, since this methodology totally relies on the experience of performers and is based on guesswork and trials, it carries risks tied to the human factor.

When implementing this methodology, specifications must be clear. The requirements must be set in a detailed and comprehensive way. Otherwise, it is impossible to create and conduct effective test scenarios, and therefore, successfully perform quality assurance.

Conclusion

The black box methodology is beneficial for various types of testing and provides its own unique advantages. It is suitable to fix flaws in the user interface or in the requirement specifications and ensures that all functions work properly. The most important feature of the black box approach is the close resemblance to hackers’ behavior, which helps to predict and prevent an attack.

Nevertheless, it is necessary to keep in mind that some errors, such as bugs in the internal code, cannot be found using only this method. Hence, to implement the most comprehensive verification, the best option is to use several types of pen testing simultaneously. To do this, make sure to delegate this task to reliable and expert testers.

At EffectiveSoft, we have built a robust Quality Assurance team to provide our clients with professional support for software testing. If you want a project estimate, don’t hesitate to contact us.