[Greylist-users] Possible Enhancements

jmr jmr at pragmagic.com
Tue Jan 25 06:53:52 PST 2005

right on!

even though i myself have never actually seen
"a poop fight in a marmoset cage",
i believe i understand your intent.

thank you bob!


Bob Beck wrote:

> > Yeah..  But the general rule of thumb is that you don't trust the From:
> > address..  So..  The only way to accomplish this would be to use the IP
> > address of the incoming connection.  Reverse lookup, MX, and callback..
> >
>         Which proves exactly nothing, if you don't trust the FROM: address,
> because of course, it's probably forged, either a Joe Job or a nice
> throwaway domain, either of which can have an MX record because
> spammers aren't stupid.  Look, it costs me nothing to register a
> throwaway domain, put some pudwanking linux box up with a mailserver
> that will answer to port 25 delivering everything to /dev/null,
> register a nice liberal SPF record for the domain for all the people
> still dumb believe that spam <-> forgery, and then buy me a nice
> bot-net of compomised broadband connected virus run time environments
> from which to fling spam at the masses faster than a poop fight in a
> marmoset cage. The box which is MX'ed to never sends one piece of spam
> - the compromised PC's do. It just sits there looking like an innocous
> mailserver, recieving all your "callbacks", (and /dev/null'ing all the
> bounces from morons with idiotically configured bounce-after-recieve
> SMTP DDOS multipliers :) At least, it does that until a different
> spammer hacks into it through linux-hole-of-week and makes it part of
> his bot-net, but that's another story :)
>         There's also of course, the case where I legitimately
> use a different host for outbound deliveries than inbounx MX. Happens
> all the time.
>         The only thing callback can concievably help you for is deciding "Am
> I talking to a real mail server" - you could connect back to the
> connecting IP, and try to issue a few simply smtp commands. However
> the problem with this is that if it works, ok, but if it doesn't, the
> lack of a connection doesnt' tell you enoug. It may simply be that the
> the outbound mailserver is firewalled inbound, etc. etc.
>         So really, you've gained not too much. Wait for the message to retry
> by conventional greylisting and you know you have at least something
> vaguely resembling a standards compliant MTA talking to you, and in the
> meantime hopefully you've considered what else he was trying to deliver
> from the same address, allowed the blacklists to catch up, etc. etc.
> etc.
>         Greylisting buys you exactly two things:
>         1) Is the sender a real queueing MTA - most virii don't currently
> retry. At least if they do, it costs them more resources on the host
> they've compromised. Remember that this only works well now because
> the majority of the world isn't greylisting, so it isn't worth a
> spammer's while to retry from a bot (yet).
>         2) Time. time to check out what else will be attempted to be
> delivered from the same host in the next 30 minutes and blackist him
> yourself, Time for him to trip over one of your spamtrap addresses in
> the next 30 minutes so you blacklist him yourself, or time for someone
> else of eminent authority to decide he's up to no good and shove him
> in your favorite blacklist... Once there, into the tarpit he goes...
>         -Bob
>         P.S. Actually, for me I get a third thing. Because my greylister *is*
> my tarpit talking fast, and I *make* it look like a spamtrap - many
> spammers programs give up when they see the banner, rather than retry
> and come through. Doesn't break my heart, they go and bother someone
> else with their hijacked bandwidth.
> --
> Bob Beck                                   Computing and Network Services
> beck at bofh.ucs.ualberta.ca                           University of Alberta
> True Evil hides its real intentions in its street address.
>   ------------------------------------------------------------------------
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dr. j. michael robinson                         jmr at mail.pragmagic.com
senior technical partner
pragMagic Inc.

           "As I would not be a slave, so I would not be a master.
            This expresses my idea of democracy.
            Whatever differs from this,
                 to the extent of the difference, is no democracy."

               - Abraham Lincoln, 1 August, 1858 -

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