What is fuzzing in cybersecurity?

If you’re new to cybersecurity or are trying to learn new skills, you may have heard cyber professionals talk about “fuzzing” or “fuzz testing.” Cybersecurity fuzzing or fuzz testing proactively identifies software vulnerabilities before malicious actors can exploit them. According to the OWASP Foundation, fuzzing is a black box approach to software testing. By injecting malformed or unintended data into software in an automated fashion, fuzzing attempts to discover unintentional behavior and impacts.

Cybersecurity professionals use fuzzing, usually in an automated process, to find weaknesses in software by feeding it unexpected or invalid inputs. It’s like poking a program with a bunch of random data to see if it breaks or malfunctions in a way that could be exploited by an attacker.

Why is fuzzing or fuzz testing important?

Fuzzing is an essential process in identifying vulnerabilities. Here are a few reasons why it’s effective:

• Uncovers unknown vulnerabilities: Fuzzing doesn’t rely on prior knowledge of specific weaknesses. It casts a wide net to find new and zero-day vulnerabilities that have yet to be documented.
• Automates testing: Fuzzing tools can run continuously, feeding the program with tons of variations of bad or invalid data, saving security professionals time and effort.
• Mimics real-world attacks: Hackers often use similar methods to exploit software flaws, so fuzzing helps simulate real-world attack scenarios.

How is fuzzing used in identifying vulnerabilities?

Fuzzing is helpful across a wide variety of cybersecurity functions and protocols. It can be used on flat files, structured data, network protocols, or data entry forms. Fuzz testing techniques vary based on file formats, protocols, or structure.

• File format fuzzing: A fuzzer can target specific file formats, like PDFs or images, by feeding the program malformed versions of those files. This can expose vulnerabilities in how the software handles unexpected data within the file format.
• Protocol fuzzing: This focuses on network communication protocols. The fuzzer bombards the program with invalid or unexpected data packets to see if the program crashes or leaks information due to improper handling of the malformed packets.
• Mutation fuzzing: This technique starts with valid inputs and modifies them in various ways. For instance, it might add extra characters, change data types, or remove required fields. This helps test the program’s ability to handle slight variations in expected inputs.
• Generative fuzzing: This advanced technique uses algorithms to automatically generate new and more complex test cases based on previous successful fuzzing attempts. This helps the fuzzer explore a broader range of potential vulnerabilities.
• Greybox fuzzing: While traditional fuzzing is black-box (no knowledge of internal code), greybox fuzzing leverages some understanding of the program’s inner workings. This can guide the fuzzer towards areas more likely to contain vulnerabilities, improving efficiency.

It’s important to note that these are just some examples, and the specific approach will depend on the protocols or software platform (e.g., Windows OS vs. Linux; TCP vs. UDP).

Learn more about fuzzing or fuzz testing!

If you’d like to learn more about fuzzing, it is an essential skill if you’re exploring the world of hacking or bug bounties. Many ethical hackers utilize fuzzing to discover vulnerabilities software companies are willing to pay bug bounty money for.

Here are a few resources to learn more:

• Cisco Talos releases Fuzzer, an open-source macOS tool for fuzzing
• OWASP Foundation: Fuzzing
• All you need to know about fuzzing and fuzz testing (Medium)
• GitLab: What is fuzz testing?
• Synopsys: What is fuzzing?

One last word of advice: You’ll find countless “boot camps” specific to fuzzing or cybersecurity online. Some can cost from a couple hundred dollars to thousands. Please do not enroll in these expensive boot camps. They are money grabs with very low returns on investment.