Mac OS X Tiger in a Nutshell

Telnet

Mac OS X versions prior to 10.1.0 shipped with telnetd , a daemon that runs the Telnet protocol, as its default remote login server. Telnet is a decades-old method for getting a virtual terminal on a remote machine through a network. However, it’s inherently insecure, because all its transmissions are cleartext, lacking any sort of encryption, and hence easily readable by malevolent entities monitoring the traffic that enters and leaves your network. Use of Telnet has, in recent years, fallen out of favor for Internet-based remote logins now that such tools as SSH are freely available.

If you must, you can run telnetd on your Mac OS X machine. You’ll find it in /usr/libexec/telnetd but won’t be able to launch it directly from there. telnetd is one of several network services, including ftpd and sshd, controlled by the super-server process xinetd, which listens on the network for service requests and launches the proper daemon on-demand. The easiest way to have xinetd begin passing Telnet requests to telnetd is to run the service command (a script, actually) as root:

    sudo service telnet start

This command modifies the proper xinet.d file (/etc/xinet.d/telnet) to enable Telnet services and then force xinetd to re-read its configuration files. Once the command is performed, any incoming Telnet requests will cause telnetd to launch and receive that connection. To turn this off, simply run the similar command:

    sudo service telnet stop

If you do enable telnetd, consider carefully ...