Great Circle Associates Firewalls
(April 1995)
 

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Subject: Re: Firewall Failure Modes
From: emwmf @ emw . ericsson . se (Martin Fredriksson)
Date: Tue, 25 Apr 95 18:19:54 +0200
To: fc @ all . net
Cc: firewalls @ GreatCircle . COM

Dr Cohen wrote:
> I am getting really confused.  A lot of people on this list seem to
> think that testing is a theoretical thing that you do to stop
> theoretical threats, and that practical programers don't need to do
> testing because they can look at their code and know it's right.

It's theoretical as long as one only talks about it.  Why don't you
publish a test specification?  That would be a real thing.

> Most of the firewall vendors and other people on this list write
> programs, never test them at the boundary conditions, and assume that
> they works properly because the code looks right to them and seems to
> work when they try it on their application.  When someone asks about
> boundary conditions, they say they have never tested it, but that they
> looked at the source code and figure it will work the same way under
> high stress conditions as under normal load conditions.

This is not the impression I have from reading this list.  Nor the
impression I get from studying parts of the fwtk.  Most programmers
probably test a lot of boundary conditions, and omit testing a lot of
boundary conditions.  Heck, we live in a real world (at least I think
so? :).

>                                                          The lack of
> experimental confirmation presents no problem for the producers or
> consumers and presents no impediment to the purchase of a firewall from
> such a vendor.

"experimental confirmation" as you well know (I gather from one of your
previous mails) has a very limited value.  Since firewalls can be very
different, and put to very different usages, I believe that the most
effective testing has to be specified by end user and has to be
performed on site.  As I wrote earlier, I'm working on a "security
policy" document which will include test specifications for different
scenarios.  I would really appreciate help, ideas, pointers, etc,
regarding this.

/// Martin F

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