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Guides

Open source and cyber security

What open source software is, whether it's safe, and which tools are most used in cyber security.

Cyber security

3 July 2025

Table of contents

  • What is open source software?
  • What does open source really mean: licenses and philosophy
  • Is open source secure?
  • The most famous open source software
  • Open source in cyber security: essential tools
  • Why businesses embrace open source?
  • Best practices for managing open source in enterprises

While many consider “open source” to be a synonym for transparency and security, it’s important to understand what the term really means. Is open source truly secure? What are the most famous examples? And how does it serve the field of cyber security?

In this article, we’ll explore the definition of open source, its implications for digital safety, highlight some of the most popular tools, and explain how it’s being used to protect systems from cyber threats.

What is open source software?

Open source software is any program whose source code is freely available for anyone to access, modify, and distribute.

Unlike proprietary software—where the code is hidden and legally protected—open source encourages collaborative development and public scrutiny.

A simple example?
Think of it like a public recipe: anyone can see the ingredients and preparation steps, suggest improvements, or tweak it to their taste. This model has led to the creation of robust, high-quality software used across the world, particularly in the cyber security industry.

What does open source really mean: licenses and philosophy

The term open source refers not only to freely available code, but to a legal and philosophical framework centered on openness, freedom, and collaboration. This is why open source has become a cornerstone of innovation in software and cyber security.

The four core freedoms

For software to be considered truly open source, it must meet four basic conditions defined by the Open Source Initiative (OSI):

  1. Freedom to use the software for any purpose.
  2. Access to the source code to study how it works.
  3. Freedom to modify the code and adapt it.
  4. Freedom to redistribute original or modified versions.

These principles promote security through transparency, allowing vulnerabilities to be identified and resolved by the community.

Key open source licenses: comparison and use cases

 GPL (General Public License)

One of the most restrictive licenses. Any software based on GPL-licensed code must also be released as open source(copyleft principle).

Real-world example
If you modify the image editor GIMP (under GPL) and create your own version, you are legally required to release your version under the GPL as well.

Example of GPL-style code:

// file: mymath.c (GPL)

int add(int a, int b) {

    return a + b;

}

You’re free to use or modify it, but redistribution must follow the GPL terms.

 MIT License

Very permissive: allows commercial use, modification, and closed-source distribution, as long as the original license notice is included.

Example
Meta’s React framework is under MIT License. You can include it in commercial apps without opening your source code.

MIT license header example:

/*

MIT License

Copyright (c) 2024 John Doe

Permission is hereby granted...

*/

function hello() {

    console.log("Hello Open Source");

}

Apache License 2.0

Similar to MIT but includes explicit patent protection—a major consideration for enterprise adoption.

Example
Projects like Apache Kafka and Apache Spark are covered under this license, encouraging corporate contributions.

Cyber security implications

Open source licenses play a key role in cyber security by:

  1. Clarifying liability
    Authors are not legally liable for vulnerabilities.
  2. Enabling custom tools
    Tools like Suricata or Wireshark can be adapted to specific corporate environments.
  3. Encouraging forks
    If a project is abandoned, anyone can fork and maintain it.

Is open source secure?

One of the most debated questions: is open source software safe? Since the code is publicly visible, doesn’t that make it easier to exploit?

The short answer is: open source can be very secure, depending on how it’s maintained. Its security lies in the principle of “security through transparency”. When many experts can audit and review code, vulnerabilities are more likely to be spotted and patched quickly.

Example
OpenSSL, the open-source cryptographic library. In 2014, the Heartbleed bug exposed a serious flaw. Because the project was open source, developers worldwide could immediately examine the problem, propose fixes, and strengthen the code.

However, security depends on the quality of maintenance. An abandoned or poorly updated open source software can represent a risk.

For this reason, it is essential to evaluate the reputation of the project, the number of active contributors, the frequency of updates and the available documentation.

famous open source software

The most famous open source software

Some open source projects have become industry standards, used by millions. Here are some notable examples:

  • Linux
    The open-source operating system that powers everything from servers to Android phones
  • Firefox
    A browser that champions privacy and open technology
  • LibreOffice
    A free and powerful alternative to Microsoft Office
  • GIMP
    Graphic design and photo editing software
  • VLC
    A media player that can play virtually any video or audio file
  • Blender
    A high-end 3D modeling and animation tool
  • Audacity
    An audio editing tool widely used for podcasts and music production

These examples show how open source can deliver professional-grade solutions across various domains.

Open source in cyber security: essential tools

In the realm of cyber security, open source tools are not just free—they’re often the industry standard.

From penetration testing to vulnerability assessment, many professionals rely on these tools daily.

1. Wireshark – Network traffic analysis

Used for packet capture, forensic analysis, and intrusion detection.

Example command:

sudo wireshark

Or from terminal with tshark:

tshark -i eth0 -Y "http.request" -T fields -e ip.src -e http.host

This command intercepts HTTP requests and prints the source IP address and host.

2. Metasploit Framework – Exploitation and testing

A robust framework with modules for exploits, payloads, and auxiliary scans.

Sample exploit scenario:

msfconsole

use exploit/windows/smb/ms17_010_eternalblue

set RHOSTS 192.168.1.10

set LHOST 192.168.1.5

exploit

Simulates EternalBlue on a target host.

3. Kali Linux – Penetration testing OS

Pre-loaded with tools like Hydra, Burp Suite, John the Ripper, and more.

Hydra example:

hydra -l admin -P /usr/share/wordlists/rockyou.txt 192.168.1.10 ssh

SSH brute-force attack.

4. Snort – Intrusion detection

Snort uses rules to detect suspicious traffic.

Example rule:

alert tcp any any -> 192.168.1.10 80 (msg:"SQL Injection Attempt"; content:"' OR 1=1"; sid:1000001;)

Flags common SQL injection patterns.

5. Nmap – Network scanner

Discovers hosts, ports, and services.

nmap -sS -sV -T4 192.168.1.0/24

Performs a stealth scan on the local subnet.

6. ClamAV – Open source antivirus

Suitable for mail servers and Linux systems.

clamscan -r /var/www

Scans a directory recursively.

7. OSSEC – Host-based IDS

Analyzes logs, detects rootkits, checks file integrity.

<rootcheck>

  <disabled>no</disabled>

</rootcheck>

8. Suricata – High-performance IDS/IPS

A multi-threaded alternative to Snort.

Start command:

suricata -c /etc/suricata/suricata.yaml -i eth0

9. OpenVAS – Vulnerability scanner

Helps identify weak configurations and outdated software.

Access via browser after setup: https://localhost:9392

10. Privacy tools

  • KeePass – Password manager
  • Veracrypt – Disk encryption
  • GnuPG – PGP for files and email
  • Tor – Online anonymity and dark web access

GnuPG encryption:

gpg --encrypt --recipient alice@example.com file.txt

Open source in enterprise environments

Today, many companies across sectors—finance, healthcare, government—are embracing open source software not only to save money, but to gain control, agility, and security in a rapidly changing digital landscape.

Why businesses embrace open source?

1. Cost savings

Licensing proprietary software often entails heavy costs. Open source reduces or eliminates this burden, freeing up resources for custom development, support, and security hardening.

Example
A financial institution replacing Oracle Database with PostgreSQL or MariaDB can cut software expenses significantly while maintaining performance.

2. Greater control and visibility

Having full access to source code allows enterprises to audit, customize, and improve the software to meet strict internal requirements.

Real-world scenario
A healthcare organization may tailor an open source Electronic Health Record (EHR) system to comply with HIPAA or GDPR by building custom data protection layers.

3. Customization and flexibility

Closed-source tools are often rigid. Open source allows businesses to build exactly what they need by modifying core features or adding plugins.

Example
A logistics company could integrate new modules into the Odoo ERP to fit its custom inventory workflows.

4. Verifiable security

Open source code is open to independent auditing, improving trust and accelerating the discovery of vulnerabilities. This aligns with industry standards such as those promoted by OWASP.

5. Avoiding vendor lock-in

By adopting open source, companies avoid becoming dependent on a single vendor, which can impose price increases, end-of-life decisions, or unfriendly licensing changes.

Best practices for managing open source in enterprises

To fully benefit from open source, enterprises must implement strong governance models:

  • Update policies
    → Use tools like Ansible, Chef, or GitOps workflows for automatic patching.
  • Staff training
    → Ensure your IT team understands Linux, Git, Docker, and secure DevOps practices.
  • Continuous security testing
    → Run scanners like Trivy, OpenVAS, SonarQube to detect vulnerabilities.
  • License compliance
    → Monitor the software stack to ensure all components follow permitted licenses.

Questions and answers

  1. What is open source software?
    Software whose code is open for anyone to view, modify, and share.
  2. Is open source always free?
    Often yes, but some versions include paid features or commercial support.
  3. Is open source more secure?
    It can be, especially with active maintenance and large communities.
  4. What are the top open source tools in cyber security?
    Metasploit, Wireshark, Kali Linux, Nmap, Snort, and OpenVAS.
  5. Can open source be used in business?
    Absolutely, with proper security and compliance measures in place.
  6. Does open source mean no licenses?
    No, it means the software is licensed to allow openness and modification.
  7. What’s the difference between GPL and MIT license?
    GPL requires derivatives to remain open source; MIT allows closed-source use.
  8. Why do hackers use open source tools?
    Because they’re powerful, customizable, and well-documented.
  9. Is Linux the most important open source project?
    It’s certainly one of the most influential, especially in enterprise and security.
  10. How can I find reliable open source software?
    Repositories like GitHub or SourceForge, looking for active projects with frequent updates.
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