SELinux (Security-Enhanced Linux) is a Linux kernel security module that provides a mechanism for enforcing mandatory access control (MAC) policies. MAC is a type of access control that restricts the actions that can be performed by processes and users on a system.
SELinux was developed by the United States National Security Agency (NSA) and was first integrated into the Linux kernel in 2003. SELinux operates at the kernel level and provides a powerful and flexible security framework that can be used to enforce a variety of security policies, including role-based access control (RBAC), type enforcement (TE), and multi-level security (MLS).
SELinux provides an additional layer of security to a Linux system by limiting the permissions of system processes and users and by isolating processes from one another. This helps to prevent malicious or poorly written software from compromising the security of the system, and helps to prevent data theft or tampering.
SELinux can be configured in different modes, including permissive, enforcing, and disabled. In permissive mode, SELinux does not enforce its policies, but it logs actions that would have been denied if the system was in enforcing mode. In enforcing mode, SELinux enforces its policies and denies actions that are not permitted.