Dictionary · Protocols and Ports
Telnet
Remote access · Beginner
A legacy remote-terminal protocol that sends commands and credentials in the clear. It remains useful only for narrow lab tests and should not manage production systems.
It lets one computer act as a terminal for another, but anyone who can see the packets can read the session. Secure remote shell replaced it for administration.
Example: A lab device still accepts cleartext terminal connections on the legacy port, so the team disables that service.
Ports
- TCP 23 — Cleartext remote terminal
Common misconception
- Seeing this protocol in a textbook does not mean it is acceptable on a modern production network.