SSH, or secure shell, is a protocol by which users can remotely log in, administer, or transfer files between computers using an encrypted transport mechanism. Running over every major operating system, SSH provides a more secure connection method than traditional telnet or the much-maligned "r commands" (rlogin, rcp, rsh). SSH includes provisions for key-based authentication that doesn't require a password, which opens the door for some innovative remote access applications.

SSH works on a client/server model. A user runs SSH client software to connect to a server running SSH software that listens on a TCP port. Like telnet, SSH gives users a command-shell type interface into the computer. Unlike telnet, SSH encrypts the login credentials and all of the data flying over the wire. SSH and its related protocols, such as Secure Copy Protocol (SCP) and Secure File Transfer Protocol (SFTP), offer more secure alternatives to their unencrypted brethren.

By Steve Suehring at NewsForge.

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