Firejail is a SUID sandbox program designed to reduce security breach risks by restricting the runtime environment of untrusted applications. The tool utilizes Linux namespaces, seccomp-bpf, and Linux capabilities to create isolated execution environments. The software provides processes and their descendants with private views of globally shared kernel resources including the network stack, process table, and mount table. It operates within SELinux or AppArmor environments and integrates with Linux Control Groups for enhanced security controls. Written in C with minimal dependencies, Firejail runs on Linux systems with kernel version 3.x or newer. The tool can sandbox various process types including servers, graphical applications, and user login sessions. It includes pre-configured sandbox profiles for common Linux applications such as Mozilla Firefox, Chromium, VLC, and Transmission. The implementation focuses on lightweight operation with low overhead, requiring no complex configuration files, socket connections, or background daemons. All security features are implemented directly within the Linux kernel and are available on standard Linux installations.