Basic Knowledge


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Trung Nguyen

CEO @CyStack|May 24, 2023

What is Fuzzing?

Fuzzing is a simple but powerful software testing technique to detect and fix vulnerabilities in software. It is an effective way to spot specific system weaknesses, such as denial of service (DoS), SQL injection, memory corruption, and buffer overflow. This testing type can be automated or manual and is typically used to test applications like servers, network protocols, file formats, and other software components.

(Example of Fuzzing for Java Application Testing)

Fuzzing Best Practice in Cybersecurity

Cyber attacks have become a big problem in today’s digital age. There have been lots of data breaches causing severe reputation or financial damage. Therefore, businesses must raise awareness and take proactive action to secure networks and systems. For example, Google Project’s Zero team has helped many conglomerates identify security weaknesses.

Furthermore, due to strict industry regulations, more companies must carry out automated testing processes before launching a software product. Some compliances and standards require businesses to integrate Fuzzing into software development, particularly in high-demand security fields like fintech or e-commerce. A famous example is ISO 27001 – a prestigious Information Security Management Systems certificate for software development services or UL2900-1 and UL2900-2-1 for Healthcare and Wellness systems. There are other standards that recommend fuzzing integration such as

  • ISO 26262
    Road vehicles – Functional Safety
  • UNECE WP.29
    United Nations World Forum for Harmonization of Vehicle Regulations
  • ISA/IEC 62443-4-1
    Secure Product Development Lifecycle Requirements
  • ISO/SAE DIS 21434
    Road Vehicles — Cybersecurity Engineering
  • ISO/IEC/IEEE 29119
    Software and Systems Engineering – Software Testing
  • ISO/IEC 12207
    Systems and Software Engineering – Software Life Cycle Processes
  • ISO 22301
    Security and Resilience — Business Continuity Management Systems
  • IT-Grundschutz (Germany)
    Based on ISO 27001
  • NIST SP 800-95
    Web Services — standard for software testing (USA) and others
  • How does Fuzzing work?

    Fuzzing provides many random or unexpected inputs to a software application to identify vulnerabilities or errors that can cause the system to crash or behave unexpectedly.
    If testers find the vulnerable point in the system, Fuzzing will also help them find the root cause of it. Fuzzing can be done manually or automatically, using specialized tools to input random or malformed data into the application or networks.

    (Simple demonstration of fuzzing process)

    Explore types of Fuzzing test

    There are several types of Fuzzing tests, depending on the specific feature of the system or application. Below are some of the popular classes that you should know.

    Protocol Fuzzing

    Protocol fuzzing is an automated and efficient type with a high-performance system environment when speed is the priority. The goal of this type is to identify the vulnerabilities of a server or system when it handles network traffic, such as Hypertext Transfer Protocol (HTTP) requests, File Transfer Protocol (FTP) commands, and TCP/IP. It sends forged network packets to the tested system and eventually serves as an intermediary, altering real-time requests and replaying them.

    File format Fuzzing

    File format fuzzing test involves sending malformed files or unexpected inputs to a targeted application and monitoring how it responds. It can test a variety of file formats, including document formats (docx, pptx), image formats (jpg, png), and audio and video formats (avi, mp4). As many companies rely on exchanging data between each component of an application or system, file format fuzzing helps identify vulnerabilities that cybercriminals can exploit.

    API Fuzzing

    By sending invalid or unusual input to a given API, testers can check whether the API has any errors, crashes, or bugs. Then they can pinpoint software flaws and have solutions to prevent any unauthorized access which criminals can exploit. However, API is not the best method to ensure the flawless security of the API. Pen-test is a higher form of testing that can provide an overview of security status.

    How to Implement Fuzzing to Improve Cybersecurity?

    Fuzzing is such a powerful method to help businesses prevent cybersecurity. The implementation of Fuzzing can be done in several steps, but you should take note of the two steps below.

    Select the proper fuzzing test

    There are many types of fuzzing tests that you can choose. First, determine which input type fits your application or system. For example, protocol fuzzing is suitable when you test network protocols. It would help if you considered the fuzzing techniques as different fuzzing testing types will use various methods to generate input. The fuzzing techniques can use machine learning or algorithms for input generation.

    Setting up a test environment

    Usually, testers will use virtual machines to set up a test environment for Fuzzing. They will create an isolated and similar production environment, including hardware, software, and network configurations. Remember that you should turn off any firewall or security measures during the fuzzing process to avoid interference.

    What Benefits of Fuzzing to Businesses?

    Fuzzing is one of the primary methods that cybercriminals use to sneak into your system. By utilizing it, you can detect hidden weak spots and prevent any potential cyberattacks. Besides this benefit, there are other benefits of fuzzing to businesses.

    Perform tests on Source Code

    While doing Fuzzing, developers can analyze the structure of the tested source code. Automated fuzzing tools can generate several test cases quickly, and they can track the paths that inputs take as they go through a program. As a result, these tools can provide comprehensive feedback on the code coverage and the specific inputs being executed during the source code testing process.

    Detect Multiple Bugs

    If, during the test, fuzzing spots an unusual input that can cause a system crash or strange behavior, it will use mutation algorithms to create extra inputs that have a high chance of reproducing the same finding. In this way, Fuzzing allows testers to discover multiple bugs or vulnerabilities in the system.

    Enable Rapid Feedback

    With fast testing speed and the ability to track code coverage, Fuzzing can provide rapid feedback to developers and testers, which can help speed up the software development process and take less time and effort required for the testing process.


    Fuzzing is an efficient and time-saving software testing technique as its ability is to speed up testing speed, reduce test cases and give developers or testers instant feedback. With the rising of cybersecurity, it is increasingly integrated into the software development process to prevent any vulnerabilities that cybercriminals can exploit. At CyStack , we are experts in software security, and Fuzzing is one of the experts. If you want to try fuzzing your software testing process, please discuss it with us.

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