mod_jail is Apache 1.3.xx/2.0.xx module, that makes running Apache in a secure jail
prison easy, so it is intended to run on FreeBSD only. It is similar to
mod_chroot, but uses FreeBSD's specific system call - jail. Also mod_jail make
it possible to change securelevel into jail prison.

WWW: http://igorpopov.newmail.ru/mod_jail/