Great Circle Associates Firewalls
(October 1995)
 

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Subject: Re: Vendor Dial-in
From: frankw @ in . net (Frank Willoughby)
Date: Mon, 9 Oct 95 15:40:02 -0400
To: Edward Maillet <maillet @ doc . cs . usm . maine . edu>
Cc: firewalls @ GreatCircle . com

You brought up a good point - and a question that is seldom raised.
In the hurry to get problems solved quickly, many people don't go 
to the trouble to think about the "what ifs" involved when vendors 
dial-in to their systems / networks.  Hats off to you for forward
thinking.

I have had to deal with this problem a number of times in a previous
life, and in a nutshell, I would be *extremely* cautious about letting 
*any* vendor log into my network to solve anything.  You have no way
of knowing (or verifying) how secure the vendor's network is, or who
the person is (could be a hacker with a daytime job).  (Also, if the 
other company had a worm running loose on their network and you connect 
the two networks together...).  8^(

In almost all situations, there are alternatives.  I would recommend
finding one that avoids having the vendor log in or at the very least
restrict things so much that the damage is contained.

A few possible ways of handling the situation (in no particular order).

1) "Sorry, but our policy doesn't allow dial-in connections".  Probably
   won't work, but it's worth a try.  The other company might even suggest
alternatives.  If they want your business, they will work with you on
   this.  If they balk, ask to log onto their network.  8^)

2) Troubleshoot the problem over the phone (like most helpdesks do).
   This assumes that the person performing the actions understands the
   technical ramifications of what they are doing.

3) The PC Anywhere idea was pretty good, but have fun trying to find someone
   to monitor the keystrokes at 2am.  Also, they person doing the monitoring
   may not necessarily understand what the vendor is doing and would not be
   in a position to detect/prevent unauthorized or malicious activities.
   Aside from that, it is a good idea.  (Friendly greetings back to Holland) 8^)

4) Create a copy of the system to be troubleshot, throw it on an isolated
   LAN (with no other systems on it, disconnect it from all other networks),
   and provide a secure dial-in service.  Don't forget to tape up and mark
   the ends of the cables so that no one accidentally connects the isolated
   LAN to your internal LAN.  Any damage is contained to the system / isolated
   LAN.

5) Have them appear on-site to solve the problem.  <== My favorite as the
   person can be identified/authenticated.

6) In all cases mentioned above, the vendor should have signed the 
   appropriate NDA, Confidentiality, and Liability forms.  The forms
   should be appropriately worded (similar to the infamous s/w license
   agreements, but with the deck stacked in your favor).  Put it in 
   writing that if anything happens, that they are responsible for 
   reinbursing you for all expenses & damages, system rebuilds, etc.

7) Tap the incoming line and have the output go to a printer (after
   writing the date/time started and initialling it).  Just remember
   that the printout must be interpreted in the proper context of 
   when the commands are given.  (There are ways to get around this,
   but not in a public forum).

8) FTP the log files to them & FTP the solution from them.  

All of the above depends on the value of what you are protecting, and 
how much management support you will receive in your wise decision to 
restrict dial-in connections.  If it was me, I wouldn't let the dial-in
connection happen if there was any alternative.

Best Regards,


Frank  




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