FLASK is an operating system security architecture used in Linux distributions FLASK stands for Flux Advanced Security Kernel that offers flexible support for the security policies. It is especially designed to provide a framework for high secure operating system. Development and implementation started with the Mach microkernel, and has since shifted its focus to the Linux operating system. FLASK is a core framework in security-focused operating systems such as NSA's Security-Enhanced Linux (SELinux), OpenSolaris FMAC and TrustedBSD. This means that SELinux can be thought of as an implementation of FLASK.