"Jailing is a mechanism to virtually change a system's root directory. By employing this method, administrators can isolate services so that they cannot access the real filesystem structure. You should run unsecured and sensitive network services in a chroot jail, because if a hacker can break into a vulnerable service he could exploit your whole system. If a service is jailed, the intruder will be able to see only what you want him to see--that is, nothing useful. Some of the most frequent targets of attack, which therefore should be jailed, are BIND, Apache, FTP, and SSH. SSHjail is a patch for the OpenSSH daemon. It modifies two OpenSSH files (session.c and version.h) and allows you to jail your SSH service without any need for SSH reconfiguration.
"To use SSHjail you need the OpenSSH source package, the SSHjail patch, and some development tools like patch and make. You also need the OpenSSL and Zlib development libraries installed in order to compile the patched SSH daemon. I've successfully installed SSHjail on CentOS 4.2 and Fedora 6 distribution; the instructions may be a bit different for your Linux flavor, but you'll get the idea..."
