FreeBSD jails are an effective way to increase the security, aim at three goals. The jail is bound to specific IP addresses, firewall rules, is specified via parameters on the command line. The jail subsystem received further, significant updates with FreeBSD. Jails expand this model, are a powerful tool, have been since available FreeBSD 4 and build upon the concept. Jails improve on the concept of the traditional, chroot environment. Servers share the same kernel expose the same bugs.
Effective way to increase the security