How to set up a telnet server..... chapter 1

Setting Up a Telnet Server

CONTENTS

* Why Set Up a Telnet Server?
* Security Concerns
* Telnet Servers Available for Windows NT
* Overview of the InterAccess Telnet Server
* Installing the InterAccess Telnet Server
* Registry Keys
* User Home Directories
* Addressing Security Concerns
* Administering the Telnet Server
* Uninstalling the Telnet Server
* Summary
* What's Next?

Unlike previous chapters, this chapter is not about an application that can be used to publish information on the Internet. Instead, it's about an NT service that can be used to make remote-system administration easier. By setting up a telnet service, you will be able to access your server for various system administration tasks from anywhere on the Internet. The chapter begins with a brief discussion about various advantages and drawbacks of setting up a telnet server. Afterwards, you will be presented with a list of telnet servers available for Windows NT. Out of these telnet servers, installation and configuration issues of Pragma Systems InterAccess telnet server will be discussed. Pragma Systems telnet server was chosen because it is robust, supports screens larger than 80 ¥ 24, and all aspects of the server can be administered via an easy-to-use graphical-user interface (GUI). It is also easy to install and configure by designating user-command shells, home directories, and shell-initializing programs. If you need information about other telnet servers listed in this chapter, please visit their respective URLs. All aspects of setting up, configuring, and administering the InterAccess telnet server will be discussed shortly. After completing this chapter, you will be able to compare features of other telnet servers with those of InterAccess and select the telnet server that best suits your needs.

Unlike the command prompt of various flavors of UNIX, Windows NT's command prompt is not very powerful. However, there are a number of ways to extend the capabilities of Windows NT's command prompt. For example, it is possible to define a special shell such as the Hamilton C Shell for Windows NT, to be used by the telnet server. By using such a command shell, you will be able to make use of powerful command-line utilities to make system-administration and -maintenance tasks easier to handle.

Before various telnet servers available for Windows NT are discussed, let's first examine why you should set up a telnet server.
Why Set Up a Telnet Server?

There are many advantages in setting up a telnet server. For example, a telnet server can be used to access your server remotely from virtually anywhere on the Internet. It is possible to use Remote Access Service (RAS) or a third-party, remote-access program to connect to an NT machine, but depending on availability of hardware, software, and other factors, you might not be able to access your server at all times. On the other hand, telnet clients are widely available; all that's usually needed is access to the Internet.

Because the telnet protocol uses clear text usernames and passwords to authenticate users, there are various security risks associated with setting up a telnet server. However, in a later section of this chapter you will be shown how to implement a solution to this problem. Although the solution presented is not very elegant, it will make sure that even if someone obtains a username and password by eavesdropping on a telnet session, the password will become useless the moment a user is authenticated. This is accomplished by using a Practical Extraction Report Language (PERL) script to implement One-Time Passwords (OTP) when users telnet into the NT server. More information about this is provided later in this chapter, in the section, "Addressing Security Concerns." Although Windows NT is an operating system that extensively uses GUIs, a number of tasks can be performed using the NT command prompt. By using various command-shell extenders, NT Resource Kit programs, and other utilities, capabilities of the NT command prompt can be further extended. Listed next are a few tasks that can be accomplished by accessing your NT machine via a telnet server.

* Stop and start services
* Add or delete users
* Change user permissions or login hours
* Copy, move, delete, and edit files
* View the contents of a text file/log file
* Check the status of your server in such areas as free memory, CPU utilization, page-file status, and so on
* Change file permissions
* Shut down/reboot server

As you can see, there are many advantages to setting up a telnet server. Soon after security concerns and various telnet servers available for NT are discussed, you will be shown how to set up a telnet server and customize it to meet your needs.
Security Concerns

At the time of this writing, all telnet servers available for Windows NT use clear-text passwords to authenticate users. Although some UNIX systems use more sophisticated user-authentication systems that validate users using a challenge/response mechanism, this feature is not yet available in telnet servers for Windows NT. It is not very desirable to use clear-text user IDs and passwords, because this can compromise the security of your NT server; a person with malicious intent can log on to your server using an intercepted username and password. To avoid such a possibility, the section "Addressing Security Concerns" will demonstrate a technique that can be used to implement OTPs on your telnet server. When OTPs are used, eavesdroppers will not be able to use user IDs and passwords of legitimate users to gain access to your server; one password is good for only one login. However, the implementation of OTPs presented in a later section is not very elaborate. Soon, you will discover what I mean by not very elaborate; however, what I am proposing is certainly better than using clear-text user IDs and passwords without any additional security.


Source...

http://docs.rinet.ru/Nt4Web/ch29.htm