Kali Linux is an open-source Debian-based Linux distribution aimed at advanced penetration testing and security auditing. It provides hundreds of tools for tasks like penetration testing, vulnerability management, and computer forensics. Kali Linux is customized for security work by having network services disabled by default, a custom kernel patched for wireless injection, and a minimal set of trusted software repositories. It is freely available, open source, and designed to help users focus on their security tasks rather than surrounding configuration.