All you need to know about Fuzzing / Fuzz Testing?

What is Fuzz testing?

With the increase in dependency on applications and programs, cyber threats have increased at their peak. Any vulnerable web app or site can distort the normal flow of the business. Any attack can also lead to damaging of business’s reputation. According to a report, the global cybersecurity market was a 161.07 billion USD market cap in 2019. According to research expectations, it will reach 363.05 billion USD by 2025, marking a compound annual growth rate of 14.5 percent during 2020–2025.

Therefore, enterprises must conduct tests like fuzzing. Adding a random value to an input field or testing the web application from a hacker’s perspective plays an integral role in securing the overall system. This article is a comprehensive guide on fuzzing or fuzz testing. If you continue reading this topic, you will comprehend how fuzzing can help secure an app or system, its types, the reasons to perform this test, and the risks associated with fuzzing.

What is Fuzzing?

Fuzzing or fuzz testing is a quality assurance technique that involves an automatic bug-detection procedure. This automated software testing technique helps to identify hackable software bugs. In this testing mechanism, the testing system will feed unexpected & invalid inputs or data to the app or program to detect code-related errors and security loopholes that might help attackers steal sensitive data. We call this test fuzzing because the technique involves giving fuzzy data or fuzzy input, creating indistinct situations to distort the app.

Fuzzing Life cycle

Cybercriminals increasingly use this technique to breach a system. On the other hand, security professionals try to defend against any attack on the app by finding and fixing them first. Some world’s greatest tech giants, like Microsoft, Google, the US Department of Defense (DoD), etc., leverage fuzzing to identify loopholes. Fuzzing is an essential phase of the web-application development life cycle & gets recognized by OWASP.

Why fuzzing became a part of web app testing?

Fuzzing caters to a wide array of benefits for web application security. Fuzz testing gives an overall idea of the mutual understanding and workflow of the app with the system. Through fuzzing, security professionals can smoothly gauge the app’s robustness and any flaw that the web app posses. The way fuzzing cybercriminals use fuzzing to target a web app; web application developers also leverage the technique to identify zero-days and other vulnerabilities. Thus experts recommend fuzzing to be a part of the software development life cycle (SDLC) while developing web applications. Since web applications have large attack surfaces, it is essential to perform fuzz testing to uncover bugs from a security standpoint that other legacy testing techniques cannot.

Types of fuzzing tools

The types of fuzz testing tools depend on the fuzzers used to test an application. Here are some of them.

1. Mutation fuzzers: Based on the supplied seed input object, they keep mutating. They do not remain limited to a specific constraint but can generate a considerable amount of unusual inputs.

2. Grammar-based fuzzers: They provide new test cases based on the supplied model. The tester specifies the input format or grammar accepted by the application. They can also determine which portion of the input needs fuzz data.

3. White-box fuzzers: In this fuzzing, the testers need access to the web application’s source code to test and reveal the bugs. Usually, the software security testers or the read team use this fuzzing technique.

4. Black-box fuzzers: In this fuzzing, the testers do not get access to the web application’s source code to find the vulnerabilities. In the black box fuzzing technique, the test mechanism will mutate inputs within the application to check how the app reacts to those inputs.

Types of web application bugs fuzzing detect

While performing fuzzing on web applications, the testing can detect the following bug types.

· In numerous applications, invalid input crashes the system or reveals the backend code, structure, or format. Fuzz testing generates invalid inputs to check for exceptions and error-handling routines.

· Fuzzing also checks for memory leaks and assertion failure. For large & complicated web applications where the bugs can cause safety issues in the app’s memory utilization, fuzzing can help detect such bugs.

· Through fuzzing, security professionals can also identify correctness bugs like poor search results (due to misuse of regular expressions and other algorithms), source code revealing crashes, corrupt databases, etc.

Risks associated with fuzzing

Although the advantages of fuzzing are endless, only relying on fuzz testing can bring threats to your web application. It cannot solve all the different web application security threats. Fuzzing is less effective when dealing with security issues that do not involve program crashes, memory leaks, etc. It is also time-consuming, and setting specific boundary values becomes problematic. If you are looking for someone who can write such articles and blogs, Contact Me.


In this complicated digital era where web applications are the face of an enterprise, fuzzing is essential to eliminate real-world and zero-day attacks, uncover vulnerabilities before app deployment and make the entire code and integrations more efficient. Fuzzing can help reduce application flaws by a significant amount. This article discussed why fuzzing is a need for web app testing, types of fuzzing tools, bugs this test can detect, and risks associated with this test.



Karlos G. Ray [Masters | BS-Cyber-Sec | MIT | LPU]

I’m the CTO at Keychron :: Technical Content Writer, Cyber-Sec Enggr, Programmer, Book Author (2x), Research-Scholar, Storyteller :: Love to predict Tech-Future