From mboxrd@z Thu Jan  1 00:00:00 1970
From: Chris Brenton <cbrenton@chrisbrenton.org>
Subject: Re: blocking by domain
Date: Sun, 13 Jun 2004 07:26:37 -0400
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To: netfilter <netfilter@lists.netfilter.org>

On Sun, 2004-06-13 at 04:29, Cedric Blancher wrote:
>
> Moreover, I
> think it would generate too much latency if you had to check DNS for
> packets at firewall level.

Not to mention the accuracy is pretty poor. Say I'm fubar.com and you
have a rule blocking traffic from my domain. I can either:

1) Not create a PTR record for my IP
2) Create a PTR calling myself www.microsoft.com or similar

Both methods will defeat a domain based filter. So blocking at an IP
level is faster and more accurate. Best bet is to just do a few whois
queries to identify the IP range for the domain and block accordingly. 

HTH,
Chris