I am listing Top 10 open source tools use by hackers:
1. Nmap Security Scanner : Use for network exploration and security auditing.
2. OSSEC : It integrates log analysis, file integrity checking, Windows registry monitoring, centralized policy enforcement, rootkit detection, real-time alerting and active response.
3. OpenVAS : It is a framework of several services and tools offering a comprehensive and powerful vulnerability scanning and vulnerability management solution.
4. Security Onion : It is a Linux distro for intrusion detection, network security monitoring, and log management.
5. Metasploit Framework : It helps verify vulnerabilities and manage security assessments.
6. OpenSSH : It encrypts all traffic to eliminate eavesdropping, connection hijacking, and other attacks.
7. Wireshark : Network protocol analyzer
8. Backtrack : It is a Linux-based penetration testing arsenal that aids security professionals in the ability to perform assessments in a purely native environment dedicated to hacking.
9. ZED Attack Proxy (ZAP) : It can help you automatically find security vulnerabilities in your web applications while you are developing and testing your applications.
10. SQLmap : It automates the process of detecting and exploiting SQL injection flaws and taking over of database servers.