TELNET

Telnet

The Telnet program runs on your computer and connects your PC to a server on the network. Typically this protocol is used to establish a connection to Transmission Control Protocol (TCP) port number 23, where a Telnet server application (telnetd) is listening. You can then enter commands through the Telnet program and they will be executed as if you were entering them directly on the server console. This enables you to control the server and communicate with other servers on the network. Telnet is a common way to remotely control Web servers. Telnet client applications are available for virtually all computer platforms.

On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer. But when accessing someone else's computer through Telnet it enables you to log on as a regular user with whatever privileges you may have been granted, to the specific application and data on that computer.

Telnet isnt very secure, because by default it does not support any encryption, even passwords and usernames are unprotected, leaving your computer succeptable to be eavesdropped by others, leaving your details at risk. Also, most versions of Telnet have no authentication that ensures a client to client connection, meaning data can be intercepted before it can reach the destination host.

Telnet was developed in 1969 and provided acess to an operating system. Experts in computer security recommend that the use of Telnet for remote logins should be stopped.
 * Telnet, by default, does not encode any data sent over the connection (including passwords), and so it is easy to eavesdrop on the communications and use the password later for negative purposes; anybody who has access to a router located on the network between the two hosts where Telnet is being used can intercept the packets passing by and obtain login, password and whatever else is typed with a packet analyser.
 * Most implementations of Telnet have no passwords or secure login options.
 * Several vulnerabilities have been discovered over the years in commonly used Telnet programs.