Telnet is an internet (TCP/IP) protocol that allows the user to connect to a remote computer. To have access to that computer, you must have permission, meaning you must authenticate to the system with a valid username and password. When you are connected to the network using telnet, you can enter commands and they will be executed as if the were being entered directly onto the server console. A telnet server, by default listens to Port 23 for incoming telnet connections.

SSH, short for Secure Shell, is a secure internet protocol for connecting to remote machines. “Secure Shell” provides strong authentication and secure communications over insecure channels. It is a replacement for rlogin, rsh, rcp, and rdist. SSH protects a network from attacks such as IP spoofing, IP source routing, and DNS spoofing. SSH provides confidentiality and integrity of data exchanged between the two computers using encryption and message authentication codes (MACs). SSH is typically used to log into a remote machine and execute commands and run console/character applications. However, it also supports tunneling, forwarding arbitrary TCP ports and X11 connections; and it can transfer files using the associated SFTP or SCP protocols. An SSH server, by default, listens on the standard TCP port 22.

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