Great Circle Associates Firewalls
(March 1996)
 

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Subject: Re: Eternal war: gateway versus filtering
From: Rolf Weber <weber @ iez . com>
Date: Fri, 8 Mar 1996 17:12:01 +0100 (MEZ)
To: frankw @ in . net (Frank Willoughby)
Cc: firewalls @ greatcircle . com (firewalls)
In-reply-to: <9603081305 . AA24667 @ su1 . in . net> from "Frank Willoughby" at Mar 8, 96 08:05:44 am

> 
> >>...but i'm sure, it's only a question of time till vendors will offer
> >>both, application level and packet filtering firewalls. 
> 
> Perhaps - although I doubt if they would incorporate both into the same
> product.
> 
that was my point to say, sorry for my unclear words.

> >>a very good argument if they are acting as a consulter, too.
> >
> 
> I disagree here.  Having the firewall vendor acting as a consultant puts
> the vendor in a conflict-of-interest situation.  (Sort of like turning
> the keys of the prison over to the inmates and telling them they are not
> supposed to leave the premises).
> 
again, i didn't say it clear enough.
if a vendor offers both, he can advise his customers much better which art
of firewall would be the best for *this* customer.
the daily maintaining of the firewall is another story.

> 
> Agreed.  Putting different levels of security in parallel will ensure
> that the weaker of the two will be used to bypass the stronger security.
>
obviously :-)

> 
> Also, it is a good idea to put an IP Packet Filter (on the Internet/untrusted
> side) in series with the firewall (with the IP Packet Filter set up so
> that it filters the exact same items as the firewall).  There are two 
> advantages to this:
> 
> o There will be an increase in performance in the firewall.  
>   Since the IP Packet Filter is blocking services that the firewall will
>   also block, the firewall won't be wasting its CPU resources blocking a 
>   connection which is going to be rejected anyway.
>
no, i disagree.
i'm watching my connection and see that 99.9% of the packets are allowed
packets (i'm filtering only the real necessary, like IP-spoofing stuff,
all the other i want to welcome at my gate :-).
(BTW, if a gate is under attack, 99.9% isn't true anymore...but you can see
it as a feature, if a gate under attack becomes slow...;-)
i'm sure the additional task, packet filtering, decreases the performance
of the whole firewall system.

> 
> o The IP Packet Filter can act as a crude (and inadequate) first layer of 
>   defense in protecting the company's networks.  If the Firewall Admin 
>   makes a mistake in setting up the firewall rules, the IP Packet Filter 
>   will help reduce the risk (somewhat) of the company's exposure to the
>   Internet.  While a successful attack is possible under these circumstances,
>   it may buy enough time for Firewall Admin to catch the mistake and take
>   appropriate corrective actions.
> 
> 
> In the above instances, a router may be sufficient to serve as the IP 
> Packet Filter (a low-cost option worth considering).  For the ultra-
> paranoid who can afford it, place a stateful IP Packet Filter in series
> between the external router & the (Applications Gateway) Firewall.
> 
true.

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.


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