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Re: forged email DSN

2005-02-26 14:03:31
On Sat, 26 Feb 2005, Brian W. Antoine wrote:

  I'm aware of what DSN's are for, stop trying to be condescending.

Sorry, you seemed to be disagreeing with my statement that DSN != reply.

  Are you ever going to send more than one warning to any given domain?

It keeps an in-memory cache of senders.  When I'm not working on it,
the milter typically runs for months at a time.  I thought about 
tracking the domain also (need to cache the specific sender anyway to avoid
redoing CBV), but so far there is no need.  Since updating the 
template at 1:45pm (2 hours ago), 1000 messages have come in (mostly rejected
as forgeries and spam), and DSNs were actually delivered to the following
senders:

PWVEVBHLYS(_at_)africaonline(_dot_)co(_dot_)zw
felicia_ellison63(_at_)greggs(_dot_)co(_dot_)uk
kgay(_at_)colleges(_dot_)com
Cleve(_at_)jsarep(_dot_)com
donpaul(_at_)starpower(_dot_)net

So I am not flooding anyones mailbox.  The DSNs do not go directly
to the postmaster, but to the purported sender.  The peak
rate for our MTA is about 40000 messages/day (typically reached
during virus outbreaks).

If there is a virus that forges %randomname(_at_)joejobbed(_dot_)com, then 
limiting the DSNs per domain could be useful, but in that case
the backscatter from my program will still be a drop in the bucket.
With a random name, most attempts will fail the CBV and get rejected.

-- 
              Stuart D. Gathman <stuart(_at_)bmsi(_dot_)com>
    Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flamis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.


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