SELinux
SELinux (Security-Enhanced Linux) is a Linux kernel security module that provides a mechanism for supporting access control security policies, including mandatory access controls (MAC). It enhances system security by enforcing fine-grained permissions beyond traditional Unix discretionary access controls (DAC), such as file permissions and user/group ownership. SELinux operates by labeling system resources (e.g., files, processes) and defining rules that specify allowed interactions between these labeled entities.
Developers should learn and use SELinux when building or deploying applications on Linux systems that require enhanced security, such as in government, financial, or high-compliance environments. It is particularly useful for isolating services, preventing privilege escalation attacks, and enforcing least-privilege principles in multi-user or containerized setups. For example, it can restrict a web server process to only access specific files, even if the process is compromised.