Sandboxing [1], or isolating processes and applications in their own environment, is a long-established practice in Linux. Unfortunately, although it is efficient, it can be difficult to configure and use. Even containers and virtual machines have not improved the process much, because they are only as secure as their configuration. What makes Firejail [2] so different is that it makes sandboxing easy and can do far more if you are willing to learn how to configure it. This simplicity has made Firejail the center of attention in less than a year.

Firejail is a structural security solution; it is configured to prevent intrusions rather than react to them the way an antivirus program does. Instead of adding daemons and other applications, it works by creating a restricted environment with its own set of solutions, running within user space and using features that are already a part of the Linux kernel, such as seccomp-bpf [3]. The result is sandboxing that requires far fewer system resources than traditional solutions, such as creating a chroot jail [4], and is easy to customize.

In fact, Firejail installs with 64 security profiles for popular applications, ranging from Firefox and KMail to XChat and Wine, as well as a generic profile used automatically for applications and processes that lack a custom profile (Figure 1). All profiles use a basic syntax with one item per line that can easily be learned by studying the profiles that are installed along with the command (Figure 2).

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