Telnet is a network protocol and software tool that enables users to remotely access and control another computer over a TCP/IP network, such as the Internet or a local area network (LAN). It provides a text-based, bidirectional communication channel, allowing users to interact with the remote system’s command-line interface as if they were physically present at the machine.
How Telnet Works
• Client-Server Model: Telnet operates using a client-server architecture. The user runs a Telnet client, which connects to a Telnet server application on the remote device.
• Connection: By default, Telnet uses TCP port 23, but connections can be made to any port if configured.
• Authentication: After connecting, the server may prompt the user for a username and password. Notably, Telnet transmits all data, including credentials, in plain text, making it insecure for sensitive operations.
• Command Execution: Once authenticated, the user can execute commands on the remote system, with results sent back to their local terminal.
Security Considerations
Telnet is considered insecure because it sends all information, including usernames and passwords, in unencrypted plain text. This makes it vulnerable to interception and eavesdropping. For this reason, Telnet has largely been replaced by more secure protocols such as SSH (Secure Shell) for most remote access needs.
Historical Context
Telnet was developed in the late 1960s and became widely used in academic and research environments to access mainframes and servers remotely. The name “Telnet” comes from “teletype network” or “terminal network,” reflecting its original purpose of providing terminal access over a network.