TOMOYO Linux is a Mandatory Access Control (MAC) implementation for Linux that can be used to increase the security of a system, while also being useful purely as a system analysis tool. It was launched in March 2003 and had been sponsored by NTT DATA Corporation, Japan until March 2012.
TOMOYO Linux focuses on the behaviour of a system. Every process is created to achieve a purpose, and like an immigration officer, TOMOYO Linux allows each process to declare behaviours and resources needed to achieve their purpose. When protection is enabled, TOMOYO Linux acts like an operation watchdog, restricting each process to only the behaviours and resources allowed by the administrator.