Great Circle Associates Firewalls
(January 1996)
 

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Subject: Re: Most Secure Unix?
From: Rolf Weber <weber @ iez . com>
Date: Wed, 31 Jan 1996 13:30:08 +0100 (MEZ)
To: spencerj @ dg-rtp . dg . com (Jon Spencer)
Cc: firewalls @ greatcircle . com (firewalls)
In-reply-to: <9601302118 . AA02298 @ tsgops . rtp . dg . com> from "Jon Spencer" at Jan 30, 96 04:18:55 pm

> 
> There is no way to build a secure environment on top of an unsecure
> environment.  That is similar to adding quality into a product after it
> is produced.  It must be built in from the bottom.
> 
> The OS *IS* the firewall, if you want it to work.  Of course, it all depends
> upon what you mean by a "firewall."  Is a firewall supposed to reduce the risk
> of attack to your system? If so, then the wise will look at the real
> statistics of risk.  Only 10% of actual security incidents are done by
> outsiders.  90% are done by insiders (75% by administrators).  (Sprint says
> up to 95% are due to insiders, and Citibank MEASURED 87% done by insiders
> in 1994.)
> 
> So, if a firewall that only protects you against outsiders works perfectly,
> you might reduce your risk by 10%.  Won't you feel nice and warm and fuzzy!?

yes, i feel :-)
if the firewall is properly configured, even insiders can't break the
firewall's security.

> 
> Another problem with firewalls being an application is that the firewall
> then does not really provide much protection for WWW sites.  Since you
> can't trust the WWW software to run on the firewall (because you can't
> trust the OS), you must either put the WWW server inside of or outside of
> the firewall.  If it is outside, then there is no protection for the WWW
> server (and I am certain that we all know of the home pages that have been
> altered by hackers).  If the WWW server is on the inside, then you must
> open a hole for anonymous users in the firewall, thus greatly reducing or
> eliminating any security it might have afforded you.

how could a firewall protect a WWW server? impossible!
the only 'secure' solution is to place it outside and insure this host as
good as possible.

> 
> Bottom line is that the firewall is COMPLETELY dependent upon the security
> provided by the OS for its own security - The firewall can be no more
> secure.  If I can break into the OS, the firewall is mine to mangle.  More
> on thsi below.
> 
> [snip]
>
> Jon F. Spencer   spencerj @
 rtp .
 dg .
 com  (uunet!rtp.dg.com!spencerj)
> Data General Corp.                  Phone : (919)248-6246
> 62 T.W. Alexander Dr, MS #119       FAX   : (919)248-6108
> Research Triangle Park, NC  27709   Office RTP 121/9
>
on a typical firewall, there only runs:
 -the kernel, i never heard of any breakin with the help of a kernel bug
 -a few harmless services such as inetd
 -the firewall software, often known, sometimes proven to be good
i trust this stuff, but not the configuration of the firewall, even not mine.
if you want a better security as such one, it's surely *not* your OS, it's
simply not to connect at all.
i don't know if your OS is more or less secure as mine. but, IMHO, it doesn't
matter. human failure, that's the point you have to take care.

rolf
-- 
-----------------------------------------
Rolf Weber <weber @
 iez .
 com> | All I ask is a chance
IEZ AG   D-64625 Bensheim  | to prove that money
++49-6251-1309-113         | can't make me happy.


Follow-Ups:
References:
Indexed By Date Previous: RE: Trusted UNIX Firewalls
From: Neil <CARSON @ rmcs . cranfield . ac . uk>
Next: Re: IPSEC == end of firewalls
From: Darren Reed <avalon @ coombs . anu . edu . au>
Indexed By Thread Previous: Re: Most Secure Unix?
From: spencerj @ dg-rtp . dg . com (Jon Spencer)
Next: Re: Most Secure Unix?
From: Chris Woods <cjwoods @ Paladin . COM>

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