[ Thanks to Doug
Vitale for this link. ]
“SSH is one of the protocols of the TCP/IP protocol suite found
at the application layer (Layer 7) of the Open Systems
Interconnection (OSI) network model. Officially specified in RFC
4251 (and later, several other RFCs) SSH functions in a way that is
similar to telnet but is far more robust and capable. SSH lets you
log in to other hosts, get a shell and execute commands on them
(for more details, read up on the concept of the OS shell), and
transfer files between hosts. The major difference between SSH and
telnet as terminal emulation protocols is that SSH utilizes
encryption and strong authentication while telnet transmits data
(including passwords) in clear text, making it vulnerable to packet
sniffing. SSH, in contrast, provides secure, reliable
authentication and communication over data channels that might not
be so trustworthy (such as the public Internet). Because the SSH
protocol encrypts the communications between network devices, it
decreases the chance of an attacker (possibly an internal user)
sniffing traffic and obtaining sensitive data such as
authentication credentials.”