Netzob

Free plan LinuxWindows

What Netzob is

Netzob is an open-source tool for reverse engineering communication protocols, generating traffic, and fuzzing. It can infer message formats and protocol state machines through passive and active processes. Its vocabulary inference learns message formats from supplied traces, while grammar inference supports semi-automatic learning of a protocol’s state machine. Once those models are inferred, the simulator can generate traffic while acting as a client, server, or both. Its fuzzing module uses protocol vocabulary and grammar to build optimized test cases through mutation or generation.

Inputs include live network traffic, PCAP captures, IPC, text and binary files, and API flows through supported file formats. Netzob can export XML, human-readable output, and Peach fuzzer formats; users can also write exporters. Its documented compatibility work includes Wireshark, Scapy, Peach, and Sulley, with the stable release changelog listing automatic Wireshark dissector and Peach fuzzer generation. Netzob runs locally on Linux and Windows and is licensed under GPLv3. The project was initiated by security auditors at AMOSSYS and the CIDre research team of Supélec to address protocol reverse engineering. Its download page identifies version 0.4.1 as the latest stable release, with listed source and Debian packages dated February 2, 2013.

Who it suits

Netzob suits security evaluators who need to examine proprietary or undocumented protocols, infer their formats and state machines, and generate traffic or fuzz cases. It is relevant to work involving its listed input types and targets, including network protocols, structured files, IPC, drivers, and devices.

What it does well

Infers message formats and protocol state machines.
Simulates traffic as a client, server, or both.
Fuzzes with mutation and generation methods.
Accepts live traffic, PCAP, IPC, text, and binary inputs.
Exports XML, readable output, and Peach formats.
Runs locally on Linux and Windows.

What to know first

The latest stable version listed is 0.4.1.
Listed source and Debian packages date to February 2, 2013.
GPLv3 licensing may not fit every project.

Plans

Plan	Billed and limits	Price
Netzob	Open source · GNU GPLv3	Free

As netzob.org lists them, read 7 Oct 2026. The maker's own page has the final word.

Getting started

Visit https://netzob.org/.
Choose the free GPLv3 plan.
Use Linux or Windows.
Download a listed source or Debian package.

Verdict

Choose Netzob for local protocol reverse engineering, traffic simulation, and fuzzing on Linux or Windows, especially when you need to derive models from traces. Look elsewhere if you need a more recently listed stable release or a license other than GPLv3.

Questions

How much does Netzob cost?

The listed plan is free.

Is Netzob open source?

Yes. It is licensed under GPLv3.

Which operating systems does it support?

Linux and Windows are listed.

What can Netzob infer?

It can infer message formats and protocol state machines through passive and active processes.

What input and export formats are listed?

Inputs include live traffic, PCAP, IPC, text and binary files, and API flows through supported file formats. Exports include XML, human-readable output, and Peach fuzzer formats; users can write exporters.

What is its latest stable release?

The download page identifies version 0.4.1 as the latest stable release. Its listed source and Debian packages are dated February 2, 2013.

Facts from Netzob's own pages

Exports: The overview lists XML, human-readable, and Peach fuzzer export formats, and says users can write their own exporter. · netzob.org, 7 Oct 2026
Fuzzing: The fuzzing module uses protocol vocabulary and grammar to generate optimized test cases, with both mutation and generation available. · netzob.org, 7 Oct 2026
Grammar inference: Netzob supports semi-automatic learning of a protocol's state machine using specific algorithms. · netzob.org, 7 Oct 2026
Input formats: The overview lists live network traffic, PCAP captures, IPC, text and binary files, and API flows through supported file formats as input sources. · netzob.org, 7 Oct 2026
Integrations: The site describes export work compatible with Wireshark, Scapy, Peach, and Sulley, and the stable release changelog lists automatic Wireshark dissector and Peach fuzzer generation. · netzob.org, 7 Oct 2026
Intended users: The overview describes Netzob as helping security evaluators create fuzzers for proprietary or undocumented protocols. · netzob.org, 7 Oct 2026
License: The site identifies Netzob as licensed under GPLv3. · netzob.org, 7 Oct 2026
Maintenance status: The download page identifies version 0.4.1 as the latest stable release and dates its listed source and Debian packages to February 2, 2013. · netzob.org, 7 Oct 2026
Platforms: The download page lists Debian-like packages, a Gentoo ebuild, an Arch Linux AUR package, and a Windows installer. · netzob.org, 7 Oct 2026
Project origin: The overview says Netzob was initiated by security auditors at AMOSSYS and the CIDre research team of Supélec to address communication protocol reverse engineering. · netzob.org, 7 Oct 2026
Protocol inference: It can infer message formats and protocol state machines through passive and active processes. · netzob.org, 7 Oct 2026
Purpose: Netzob is an open source tool for reverse engineering, traffic generation, and fuzzing of communication protocols. · netzob.org, 7 Oct 2026
Support: The community page directs users to public announce and user mailing lists and an IRC channel for community support. · netzob.org, 7 Oct 2026
Traffic simulation: Given inferred vocabulary and grammar models, the simulator can act as a client, server, or both to generate communication traffic. · netzob.org, 7 Oct 2026
Vocabulary inference: Its vocabulary inference learns message formats from supplied traces using specific algorithms. · netzob.org, 7 Oct 2026

Where Netzob stands on Freedom251

Fuzz Testing Software#15 of 26