[Full-disclosure] Re: Reverse dns (whether you want it or not)

From: Dave Korn (davek_throwaway_at_hotmail.com)
Date: 03/11/05

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    To: full-disclosure@lists.grok.org.uk
Date: Fri, 11 Mar 2005 13:48:05 -0000

    "TheGesus" wrote in message news:5e70f65305031013083747d7b@mail.gmail.com...
    > On this subject (marginally), last year we moved a rather large CIDR
    > block from one ISP to another.
    >
    > The new ISP took it upon themselves to give *ALL* our unused IP
    > addresses a bogus reverse lookup in the (general) format of
    >
    > 10.20.30.40.abc.domain.com
    >
    > No one asked them to do this (or, at least if they did, they won't
    > admit to it), and none of the reverse lookups can be looked up
    > "forwardly".
    >
    > Is this a common practice? It doesn't seem like a good idea, but the
    > ISP insisted it was a "value-added" service. In my opinion, a dead
    > address should remain dead.

      It's common. ISPs don't want to have to update their DNS records with
    every single client that logs on or off their network, that would be a lot
    of churn and general overhead for no great purpose.

      Plus it's always good to avoid leaking information. If a lot of those
    machines have firewalls that block ping etc, to present a 'stealthed' low
    attack profile to the world, it would be a shame to give away the
    information about which IPs were genuinely dead and which were firewalled
    off but had live machines behind them to anyone who wanted to look it up in
    the DNS.

        cheers,
          DaveK 

    -- 
Can't think of a witty .sigline today....
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