"Summary: Security always requires a multi-layered scheme. SSH is a good example of this. Methods range from simple sshd configuration through the use of PAM to specify who can use SSH, to application of port-knocking techniques, or to hide the fact that SSH access even exists. Applying these techniques can make life much harder for possible intruders, who will have to go past three unusual barriers.
"Introduction
"If you require remote access to your computer and you enable Secure Shell (SSH) connections, you must accept that you will automatically attract hackers who will try to break your defenses and take command of your machine. Although there's no guarantee that your machine won't be "0wn3d" by a "h4x0r," a few simple solutions can help reinforce your SSH door and make life a bit more difficult for anybody trying to break in. This article considers three such techniques:"
