News Group Posts

value of firewalls, testing firwwalls

Date: Wed, 25 May 2005 05:42:36 -0400
From: Tony Lawrence <foo@pcunix.com>
Subject: Re: SCO 5.0.7 AS FIREWALL

Jeff Liebermann wrote:
> On Tue, 24 May 2005 17:47:56 -0400, Tony Lawrence <foo@pcunix.com>
> wrote:
> 
> 
>>My purpose is simply to protect myself from my own stupidity (an 
>>abundant supply of that is always stocked), though it does help that I 
>>can upgrade or temporarily disable any component without worrying much 
>>about what will happen.  On the con side, when I do want to let 
>>something in, it becomes a real PITA - but it should be, imho.  I had 
>>quite an argument about just this subject recently: see 
>>The value of firewalls
> 
> 
> Nice article.  I consider a minimal hardware firewall to be a basic
> pre-requisite to being on the internet, even if the benifits are
> dubious.  My office LAN is similar to yours.  Double NAT firewall with
> the important office machines on the inside of the 2nd layer of
> firewalls.  This mess is necessary because I'm constantly bringing
> customers virus and worm infected machines into the office and don't
> need them attacking my office servers.  However, this is an unusual
> situation that I would not expect to be popular.
> 
> Also, firwalls tend to have their own security issues.  I suggest
> running the firewall tests at:
>  http://www.pcflank.com/exploits.htm
> and see how well you do.  My Linksys BEFW11S4v4 hangs on 2 of the
> tests.  My Linksys WRT54gv1.1 with Sveasoft Alchemy firmware, passes
> all the tests.
> 
> 

Thanks for that link.

I still don't agree that the benefits are dubious.  My major argument is 
that anyone can screw up - me, the guy who writes the fw firmware, your 
cat, the neighbors dog - we all make mistakes.  If the fw people 
accidentally pass port 22 from an address I didn't approve, my sw filter 
rules hopefully still reject it.  If I bollixed that or accidentally 
disabled the whole thing, hopefully my ssh config will still protect me. 
  If there's some new bug in ssh that nobody knew about, maybe one of my 
pam rules will help me or my snort logging will let another part of my 
defenses kill the session.

The guy I was arguing with says that I might as well worry about a red 
headed nun with a machine gun bent on my demise, but I don't agree: 
maybe HE doesn't make mistakes, but I sure do, and so do most of the 
people I know.  I have no reason to believe that fw engineers or the 
authors of the sw filters etc. are immune to that.

-- 
Tony Lawrence
Unix/Linux/Mac OS X  resources: http://aplawrence.com
 

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