Open Box and Closed Box Testing: Outlining the Difference Between Them

Security testing is a crucial step of the software development life cycle (SDLC) because it ensures that the software development process and application deployed in the production environment are secure. An ideal security testing process is a holistic approach that involves various testing techniques.

The two most common security testing approaches are open box testing and closed box testing. Let’s check out what these testing methods are for and what the differences between them are.

What is Open Box Testing?

Open box testing, also known as transparent box or glass box testing, is a security testing technique where the internal code is visible to the tester. It primarily focuses on strengthening security, verifying the flow of inputs and outputs through the application, and improving the usability and design of the software.

By conducting open box testing, testers can analyze coding practices, data flow, information flow, control flow, and error and exception handling within the system, to verify the intended and unintended behavior of the software before it is deployed in the production environment.

Conducting proper security testing before launching the software helps you overcome security issues that might hamper the functionality of the application at a later stage. Security flaws in any software can be classified as major or minor depending on the risk profile of the web application.

The first step in open box testing is to assess the source code, analyze available design documentation, and other relevant development artifacts, to evaluate the security levels of software.

Second, the testers should be able to think like an attacker to create test cases that exploit software. Third, testers should be familiar with different techniques and tools available for open box testing to perform testing on software and web applications effectively.

Types of Open Box Testing

Open box testing consists of various testing techniques used to assess the security and usability of a block of code, an application or a specific software package.

Open box testing usually includes source code reviews, both manually and automatically using SAST tools. Additionally, tests against the running application may be conducted where specific functionality is tested for security defects.

Unit Testing

Unit testing is typically the first type of testing done on an application. It is performed on each block or unit of code as it is developed. It is the responsibility of developers to ensure that thorough unit testing is done to verify if the code is working as intended.

Let’s suppose that, as a software developer, you develop a code, a single object, or a function, and want to know if the code you have written is functioning properly. You conduct unit testing on the code to ensure it works appropriately before you jump into the next section and start coding further.

Unit testing helps facilitate the quick identification of security vulnerabilities early in the software development life cycle (SDLC). If you are able to identify security issues early through testing, then you can easily fix them in your software.

Testing for Memory Leaks

Memory leaks are hard to detect and tend to impact the entire application by making it run slower. Unless testing is performed at a basic level, memory leaks could exist in an application and cause various problems.

Open box testing helps identify potential memory leaks in a software application. An experienced quality analyst (QA) who knows how to detect memory leaks plays an important role in cases where applications or software are running slow.

What are the Advantages of Open Box Testing?

• Open box testing can begin in the early stages of the SDLC focusing on independent code units.
• Since the tester is familiar with the functionality of the code, designing test cases becomes easier for effective testing.
• In open box testing, the tester can easily trace back to the original source of the issue, thus helping the tester quickly fix the problem.
• Helps identify “unintended” features in the software that may be introduced during implementation and impact the security of the software.
• Open box testing can be more easily automated.
• It can direct security engineers to problematic areas of code where security controls may be in place but are not fully effective. These can be more easily identified by looking at the code than by testing it dynamically.

What are the Disadvantages of Open Box Testing?

While open box testing may sound like the ideal way to test your software applications, it does have its fair share of drawbacks. The most prominent disadvantages of open box testing are:

• Open box testing can be time-consuming and expensive.
• Every time the code of a software solution is modified, test cases may have to be rewritten completely, which is a tedious process.
• Open box testing requires people who understand code and security in software programs and this is a harder skillset to find.
• If you have a large amount of code for an application, it is very difficult to cover each and every aspect of it in a timely manner with open box testing.

What is Closed Box Testing?

Closed box testing is a fundamental part of routine security testing activities. It is a high-level security testing technique which aims to evaluate the security of the application without actually looking into the internal structure of the software application.

In open box testing, the testers are familiar with the internal architecture of the software being tested, but they aren’t in closed box testing. This may lead to them missing security vulnerabilities in the software as they may not fully understand the flow as well as someone who can read what the code is doing (as in open box testing).

In closed box penetration testing, the testers can conduct testing just like an attacker would carry out an attack. This way, testers can discover security vulnerabilities when the software application is running in the production environment.

Primarily, the closed box pen test helps identify a wide range of security vulnerabilities in a software solution such as server misconfiguration, input or output validation issues, and other problems that may be encountered in the runtime.

Types of Closed Box Testing

There are many types of closed box testing used to assess software applications, but here are some of the major ones that you should know about:

Closed Box Penetration Testing

In closed box penetration testing, the tester does not need to have prior information about the application being tested and can perform testing keeping it as real as an attacker-led scenario. It enables the security tester to think out-of-the-box and perform tests according to their practical knowledge and expertise.

Testers use all tricks and methodologies at their disposal to emulate the expertise level, knowledge, and persistence of potential attackers.

From remote access exploitation to brute force attacks, testers would make real-life attempts to breach security. The end goal of closed box penetration testing is to verify the integrity of the software applications and proactively identify security risks that pose a direct threat from an attacker.

Regression Closed Box Testing

Regression closed box testing is done whenever the internal structure of the application is altered to ensure its functionality and behavior is working as intended. The alteration could be code fixes, upgrades, or any other debugging/maintenance processes.

The software tester ensures the new code does not impact the existing security of the application. Frequent security tests are conducted to analyze if an upgrade has impacted the security of the application.

What are the Advantages of Closed Box Testing?

• Since the application is tested from the outside only, the tester does not need to have knowledge of software programming languages or specific technical skills to perform closed box testing.
• Closed box testing is an effective testing method for complex and large applications.
• Testers try various techniques to try to break into the application to simulate actual attacks to look for unexpected results.
• Common security vulnerabilities such as SQL injection, CSRF, XSS, etc. are extensively checked with this testing method
• Closed box testing also helps check for server misconfiguration issues
• Test cases for open box testing can be designed immediately after the completion of development and specifications.

What are the Disadvantages of Closed Box Testing?

• Closed box testing tends to overlook potential security vulnerabilities that may be caused due to a lack of secure coding practices or design in the application. For example, cryptographic issues are hardly ever identified in closed box testing, and they only are for the most gross defects
• This testing method does not provide the exact source of the security issue, so developers have to invest time into identifying the location of the security vulnerabilities identified in closed box testing.
• Test cases for closed box testing can be redundant if clear and concise specifications are not designed.
• Some types of vulnerabilities in a software solution are extremely difficult or impossible to detect with closed box testing, e.g., cryptography errors.

Key Differences Between Open Box Testing and Closed Box Testing

• In open box testing, the tester is required to have software programming knowledge of the application whereas in closed box testing, the tester doesn’t require programming knowledge to analyze the application.
• Open box testing is performed with the knowledge of the internal structure of the application, whereas, closed box testing is done without the knowledge of the internal structure of the software application.
• Open box testing is focused on the code conditions, structure, branches and paths, whereas closed box testing is focused on the functionality and behavior of the application.
• Open box testing provides high granularity test reports, whereas closed box testing provides low granularity test reports.
• Open box testing is a time-consuming and exhaustive process, whereas closed box testing is a less time-consuming and exhaustive process,
• Open box testing is done at the lower levels of testing such as unit testing and integration testing, whereas closed box testing is done at a higher level testing such as system testing, acceptance testing, security testing, etc.

Takeaways

Open box testing and closed box testing are both important for enterprise applications. You can easily integrate open box tests with your closed box tests and run the entire suite in minutes, prior to pushing a new application or software solution built into the production environment.

The combination of these two testing methods will help ensure the software application is not just functioning and behaving as intended, but also ensures that it is secure. Having security vulnerabilities in your application can make it susceptible to attacks such as SQL Injection, XSS, DDoS, etc.

At Cypress Data Defense, we have created and optimized security testing using various testing methods through automation testing, manual testing, and artificial intelligence. We help enterprises secure their SDLC processes and applications, with significantly cost-effective methods.

If you are interested in learning more about Cypress Data Defense, please reach out to us at info@cypressdatadefense.com.