The threat landscape is evolving fast. Here are five free, open-source tools every builder and defender should have loaded in their stack right now.

1. Wazuh — Open-Source SIEM & XDR
2. Wazuh is a full-featured SIEM platform with threat detection, integrity monitoring, incident response, and compliance tools built in. It’s free, self-hostable, and used by thousands of enterprises. If you’re building a security posture from scratch, Wazuh is your command center.
3. 2. CrowdSec — Collaborative Threat Intelligence
4. CrowdSec is a modern, open-source intrusion prevention system that shares attack signals across its global network. When one node detects a threat, all nodes benefit. It’s lightweight, integrates with firewalls, and has a growing library of threat scenarios.
5. 3. Velociraptor — Endpoint Visibility
6. Velociraptor gives you deep endpoint visibility for digital forensics and incident response. It runs hunts across thousands of machines in seconds, collects forensic artifacts, and helps you answer “what happened and when” with surgical precision.
7. 4. Nuclei — Vulnerability Scanner
8. Built by ProjectDiscovery, Nuclei is a fast, template-based vulnerability scanner used by bug bounty hunters and red teams worldwide. Its community maintains thousands of detection templates for CVEs, misconfigurations, and exposed panels. Scan your infrastructure before attackers do.
9. 5. OpenCTI — Cyber Threat Intelligence Platform
10. OpenCTI lets you structure, store, and visualize cyber threat intelligence. Connect threat feeds, track adversaries, and map attack campaigns using the MITRE ATT&CK framework. It’s the intelligence layer that ties everything else together.
11. All five of these tools are free, actively maintained, and battle-tested. BAABAA tracks updates and new releases across each — check our Free Tools Directory for the latest builds and deployment guides.