[99249] in North American Network Operators' Group
Re: Criminals, The Network, and You [Was: Something Else]
daemon@ATHENA.MIT.EDU (Stephen Satchell)
Wed Sep 12 11:55:50 2007
Date: Wed, 12 Sep 2007 08:54:56 -0700
From: Stephen Satchell <list@satchell.net>
To: nanog@nanog.org
In-Reply-To: <20070816.224345.29751.10@webmail05.lax.untd.com>
Errors-To: owner-nanog@merit.edu
My mail servers return 5xx on NXDOMAIN. If my little shop can spend not
too much money for three-9s reliability in the DNS servers, other shops
can as well. When I first deployed the system, the overwhelming
majority of the rejects were from otherwise known spam locations
(looking at Spamhaus, Spamcop, and a couple of other well-known DNSBLs).
The number of false positives were so small that whitelisting was easy
and simple to maintain.
If a shop is not multihomed, they can contract with one or more DNS
hosts to provide high-availability DNS, particularly for their
in-addr.arpa zones.
It's not hard. Nor expensive.
Paul Ferguson wrote:
> Re-sending due to Merit's minor outage.
>
> - ferg
>
>
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> - -- Robert Blayzor <rblayzor@inoc.net> wrote:
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>> The fact that they're rejecting on a 5xx error based on no DNS PTR is a=
>
> bit harsh. While I'm all for requiring all hosts to have valid PTR
> records, there are times when transient or problem servers can cause a
> DNS lookup failure or miss, etc. If anything they should be returning a=
>
> 4xx to have the remote host"try again later".
>
> Oh, wait till you realize that some of the HTTP returns are bogus
> altogether -- and actually still serve malware.
>
> It's pretty rampant right now. :-/
>
> - - ferg
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> --
> "Fergie", a.k.a. Paul Ferguson
> Engineering Architecture for the Internet
> fergdawg(at)netzero.net
> ferg's tech blog: http://fergdawg.blogspot.com/
>
>
>
>
