“If you’re a Linux administrator and you’re still using telnet
for authentication, your network could be in danger. Telnet passes
your user IDs, password/passphrase, and the content of your
terminal sessions in the clear, where anyone with a sniffer can see
what you’re doing regardless of whether they have your
password.”
“Secure Shell (SSH) is a protocol for secure terminal sessions
over the Internet. This means you can control who gets into your
servers with strong cryptography, keep passphrases from being
transmitted in the clear over the Internet, and strongly encrypt as
well as compress terminal sesions as they happen.”
“Although the Internet Engineering Task Force’s Secure Shell
working group (SECSH) has yet to publish any formal SSH standards,
SSH version 2 is currently documented in draft form and has been
implemented both by commercial and open source developers. (SSH
version 1 is a different protocol with the same goals; it is still
widely supported.)”