Kali Linux is a Debian-derived Linux distribution designed for digital forensics and penetration testing. It is maintained and funded by Offensive Security Ltd. Images are available for the Raspberry Pi.
As the distribution’s developers, you might expect us to recommend that everyone should be using Kali Linux. The fact of the matter is, however, that Kali is a Linux distribution specifically geared towards professional penetration testers and security specialists, and given its unique nature, it is NOT a recommended distribution if you’re unfamiliar with Linux or are looking for a general-purpose Linux desktop distribution for development, web design, gaming, etc.
Even for experienced Linux users, Kali can pose some challenges...
If you are new to both the Pi and linux, don't start here!