SSH

Secure Shell or SSH is a network protocol that allows data to be exchanged using a secure channel between two networked devices. [1]

Used primarily on Linux and Unix based systems to access shell accounts, SSH was designed as a replacement for TELNET and other insecure remote shells, which sent information, notably passwords, in plaintext, leaving them open to interception.[2] The encryption used by SSH provides confidentiality and integrity of data over an insecure network, such as the Internet.

http://en.wikipedia.org/wiki/Secure_Shell