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What is Fuzzing?


Fuzzing or fuzz testing is a quality assurance technique involving an automatic bug-detection procedure. This automated software testing technique helps identify hackable software bugs. In fuzzing, the testing system feeds unexpected and invalid inputs or data to the app or program. This testing helps 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.

While cybercriminals use this technique to breach a system, security professionals leverage it to find and fix hackable bugs. Tech giants like Microsoft, Google, and the US Department of Defense (DoD), among others, leverage fuzzing to identify loopholes. Fuzzing is an essential phase of the web-application development lifecycle recognized by the OWASP.

Why is fuzzing important?

Fuzzing gains importance in the backdrop of a sharp increase in cybersecurity incidents. Besides inflicting monetary damages on organizations, cybersecurity incidents wreak havoc on their reputation and draw regulatory intervention. All these scenarios adversely affect the future of the company. This exponential rise in threat has pushed the growth of the cybersecurity market. According to a report, the global cybersecurity market will likely touch US$ 363.05 billion by 2025.

Most cybersecurity professionals leverage fuzzing to strengthen enterprise security. 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. 

Why fuzzing became a part of web app testing?

Fuzzing delivers a wide array of benefits for web application security. Fuzz testing gives an overall idea of the app's workflow, reveals exploitable bugs, and helps security professionals make the app more robust. Like cyber criminals using fuzzing to target a web app, web application developers leverage the technique to identify zero-days and other vulnerabilities. 

For this reason, experts recommend that fuzzing be part of the software development life cycle (SDLC) while developing web applications. Since web applications have large attack surfaces, performing fuzz testing is essential to uncover bugs 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 examples: 

  1. Mutation fuzzers: Mutation fuzzers work on the premise that attackers have some inkling about the input format of the program under test. Minor changes are introduced to inputs to elicit new, unpredictable behaviour.

  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 red 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 and 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, and corrupt databases.

Risks associated with fuzzing

Although the advantages of fuzzing are endless, only relying on fuzz testing can bring threats to your web application. It can only solve some of the web application security threats. Fuzzing is less effective when dealing with security issues that do not involve program crashes and memory leaks. It is also time-consuming, and setting specific boundary values becomes problematic.


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. They also help uncover vulnerabilities before app deployment and make the entire code and integrations more efficient. Fuzzing can help reduce application flaws by a significant amount. To learn more about fuzzing, contact Packetlabs.

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