networking protocol used for remotely accessing a computer system.

The first version of Telnet resulted from work on ARPANET, the precursor to the Internet (see DARPA (Defense Advanced Research Projects Agency)), in the late 1960s. Computer users needed a way to remotely connect different types of computers. In response a committee of researchers from industry and academia developed the first proposal for the Telnet protocol in 1971 and produced the first version of Telnet in 1983. Since then, Telnet has been revised several times and has seen tremendous growth in its use.

Telnet relies on a Network Virtual Terminal, an environment where different computers use the same rules to communicate. This helps overcome communication differences between different computers, and the feature allowed Telnet to grow beyond simple remote access over the years. Bulletin board systems (BBSs), library card catalogs, and text-based games are just a few of the uses found for Telnet. Many of these uses are now carried out by Web-based systems, but Telnet is still used extensively.

Telnet does have its shortcomings. Many computer scientists consider Telnet a security risk. Telnet sends everything as plain text, which means that anyone can read what is sent. This also means that an intruder can exploit any potential bugs in the Telnet program to access restricted systems. Thus, many experts recommend disabling Telnet and switching to Secure Shell (SSH), a remote access protocol that encrypts all traffic. Because of this, SSH could conceivably replace Telnet as a remote access tool in the near future. This, combined with the reduction in other uses for Telnet, makes the future of the protocol uncertain.