Kali Linux is preinstalled with over 600 penetration-testing programs, including nmap (a port scanner), Wireshark (a packet analyzer), John the Ripper (a password cracker), Aircrack-ng (a software suite for penetration-testing wireless LANs), Burp suite and OWASP ZAP (both web application security scanners). Kali Linux can run natively when installed on a computer's hard disk, can be booted from a live CD or live USB, or it can run within a virtual machine. It is a supported platform of the Metasploit Project's Metasploit Framework, a tool for developing and executing security exploits.
It was developed by Mati Aharoni and Devon Kearns of Offensive Security through the rewrite of BackTrack, their previous forensics Linux distribution based on Ubuntu. The third core developer Raphaël Hertzog joined them as Debian expert.
Kali Linux is based on Debian Wheezy. Most packages Kali uses are imported from the Debian repositories.
Kali Linux is developed in a secure location with only a small number of trusted people that are allowed to commit packages, with each package being signed by the developer. Kali also has a custom built kernel tha is patched for injection. This was primarily added because the development team found they needed to do a lot of wireless assessments.