BackTrack was a Linux distribution that focused on security, based on the Knoppix Linux distribution aimed at digital forensics and penetration testing use. In March 2013, the Offensive Security team rebuilt BackTrack around the Debian distribution and released it under the name Kali Linux

History
The BackTrack distribution originated from the merger of two formerly competing distributions which focused on penetration testing:

- WHAX: a Slax-based Linux distribution developed by Mati Aharoni, a security consultant. Earlier versions of WHAX were called Whoppix and were based on Knoppix.
- Auditor Security Collection: a Live CD based on Knoppix developed by Max Moser which included over 300 tools organized in a user-friendly hierarchy.

On January 9th, 2010, BackTrack 4 improved hardware support, and added official FluxBox support. The overlap with Auditor and WHAX in purpose and in collection of tools partly led to the merger. The overlap was done based on Ubuntu Lucid LTS starting from BackTrack 5.

Tools
BackTrack provided users with easy access to a comprehensive and large collection of security-related tools ranging from port scanners to Security Audit. Support for Live CD and Live USB functionality allowed users to boot BackTrack directly from portable media without requiring installation, though permanent installation to hard disk and network was also an option.

BackTrack included many well known security tools including:
- Metasploit for integration
- Wi-Fi drivers supporting monitor mode (rfmon mode) and packet injection
- Aircrack-ng
- Reaver, a tool used to exploit a vulnerability in WPS
- Gerix Wifi Cracker
- Kismet
- Nmap
- Ophcrack
- Ettercap
- Wireshark (formerly known as Ethereal)
- BeEF (Browser Exploitation Framework)
- Hydra
- OWASP Mantra Security Framework, a collection of hacking tools, add-ons and scripts based on Firefox
- Cisco OCS Mass Scanner, a very reliable and fast scanner for Cisco routers to test default telnet and enabling password.
- A large collection of exploits as well as more commonplace software such as browsers.
- Armitage - java frontend to Metasploit.

BackTrack arranged tools into 12 categories:
- Information gathering
- Vulnerability assessment
- Exploitation tools
- Privilege escalation
- Maintaining access
- Reverse engineering
- RFID tools
- Stress testing
- Forensics
- Reporting tools
- Services
- Miscellaneous