Telnet
In a Nutshell - CIW Course Section 3, Part B1, Chapter 11
Telnet Overview
Telnet is a character-based terminal emulation package, it is also a standard protocol of the TCP/IP suite native to Unix and Windows operating systems. Telnet is used to access data and applications at a specific computer from a remote location. Telnet operates, by default, over port 23.
On a Windows 2000 server, Telnet will be installed by default, but it will not be running. You will need to configure it from the server hosting the service. Click Programs | Administrative Tools | Telnet Server Administration and you should be presented with a screen like the one below:
Type 4 and press <Enter>. This will start the Telnet service. This can also be accomplished by using the Services utility to start the service and set it to Automatic, so that it will start after a server reboot.
Now, if you type 3 and press <Enter> you will be presented with a new menu to display / change registry settings. Type 7 and press <Enter>. This will show the current NTLM value and prompt for a new value. Valid values are: 0, 1 and 2.
Level 0 - Checks the Security Accounts Manager (SAM) of the local server. Uses no encryption.
Level 1 - Uses Windows 2000 Domain Controller authentication and encrypts data. If there is no DC present then it reverts to Level 0 behaviour.
Level 2 - Uses ONLY DC authentication. All data is encrypted.
Changes made to registry settings will take effect only after the service has been stopped and restarted.
Telnet Access in Linux
There are three ways to control Telnet access: edit the Pluggable Authentication Modules, use xinetd, or use the /etc/hosts.allow and /etc.hosts.deny files.
Administering Windows 2000 using Telnet
When you connect to a remote server using Telnet, you are effectively using that server's command line interface. So any commands that can be entered from the DOS prompt may be executed via the Telnet session.
As demonstrated above, the FTP service has been stopped on the remote server. Equally, any other service may be stopped or started and many other commands can be executed from here. To be perfectly honest, I can't imagine using this much for Windows administration as Remote Desktop will be much easier. It is useful for administering non-windows systems.