Kali Linux is a GPL-compliant Linux distribution built by penetration testers for penetration testers with development staff consisting of individuals spanning different languages, regions, industries, and nationalities. The evolution of Kali took place over many years of development, penetration tests, and unprecedented help from the security community. Kali Linux originally started with earlier versions of live Linux distributions called BackTrack, Whoppix, IWHAX, and Auditor.
When it was initially developed, Kali was designed to be an all-in-one live CD to be used on security audits and was specifically crafted to not leave any remnants of itself on the system. With millions of downloads, it has become the most widely adopted penetration testing framework in existence and is used by the security community all over the world.