full-disclosure - Reverse dns

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From: simon.biles at gmail.com (Simon Biles)
Subject: Reverse dns

All other debates about it being required or not aside, I recently was
working with someone for whom reverse DNS stopped working properly for
a period. They found that although it didn't "break" some protocols, a
large number of things slowed down while a reverse DNS request timed
out these included ssh and ftp.

Additionally some website authentication mechanisms make use of a
reverse DNS lookup as part of their security, so these would be
affected as well.

Cheers,

Si 


On Thu, 10 Mar 2005 16:35:49 -0500, Valdis.Kletnieks@...edu
<Valdis.Kletnieks@...edu> wrote:
> On Thu, 10 Mar 2005 11:30:51 CST, Paul Schmehl said:
>  give details.  I'll give you this much.  We're having a
> > philosophical disagreement about the value of disallowing reverse dns for
> > hosts on our network.  It's the ancient security by obscurity discussion.
> >
> > My concern is that we should not disable dns when (or if) it's required.
> > Obviously we would not disable it for the MX hosts, but I'm unclear what
> > (if anything) the RFC requirements are.  Absent any requirements, there's
> > not cogent argument for *not* doing it, with the aforementioned exceptions.
> 
> The security via obscurity is very slim - remember that if they're looking for
> the PTR entry, they *already* have the IP address..
> 
> One good reason to put the PTR out there is because it allows sanity-checking of
> your DNS - if you have 'foo.example.com A 10.10.100.1', then there should be
> a '1.100.10.10.in-addr.arpa PTR foo.example.com' to match.  If you fumble-finger
> and get 'foo.example.com A 10.10.100.10', you can catch it because when you
> look up the PTR, you find '10.100.10.10.in-addr.arpa PTR bar.example.com'.
> 
> 
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-- 
Simon Biles
CISSP, OPSA, BS7799 Lead Auditor, MBCS