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From: woodcock@mentor.cc.purdue.edu (Bruce Sterling Woodcock)
Newsgroups: comp.unix.wizards
Subject: Re: Limiting Telnet Access
Keywords: 3b2 telnet
Message-ID: <13248@mentor.cc.purdue.edu>
Date: 6 Jun 91 07:49:09 GMT
Article-I.D.: mentor.13248
References: <27103@adm.brl.mil> <1991Jun4.230509.3655@mnemosyne.cs.du.edu>
Organization: Nicer Mudders for a Better Tomorrow, Inc.
Lines: 35

In article <1991Jun4.230509.3655@mnemosyne.cs.du.edu> jscott@isis.UUCP (James Scott) writes:
>Anyway, this is our solution:
>1.) Make a group called 'telnet'.
>2.) chgrp telnet /usr/bin/telnet .
>3.) chmod o=,gu=rx /usr/bin/telnet .
>4.) Edit your /etc/group file, adding the login names of users who 
>	can use telnet into the last field seperated by commas.
>5.) For someone to use telnet, they must first type the command
>
>	$ newgrp telnet
>and _then_
>	$ telnet
>
>NOTE: the newgrp command CAN NOT be used in a shell script.
>k

I don't think this solves the problem.  Anyone with a little knowledge of
programming... hell, even with a little knowledge of ftp... can use their 
own copy of telnet or some other client to interface to the net.  Sure, it
may slow down some people at first, but once word gets out that so-and-so
has their own telnet program, you'll be right back to the same situation.

My advice:  If you want to restrict TCP/IP, remove your machine from the
network.  Restricting net access to the users is not a very sensible thing,
usually, or a nice one.  If you *do* want to restrict it, do some kernel
hacking.  I know of several universities that have restricted the network
system calls in this way.

Bruce

-- 
|    woodcock@mentor.cc.purdue.edu    | "That's Bruce for ya, always jumping | 
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