bugtraq - RE: Is predictable spam filtering a vulnerability?

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Message-ID: <C823AC1DB499D511BB7C00B0D0F0574C584C1A@serverdell2200.interclean.com>
Date: Fri, 25 Jun 2004 16:11:53 -0400
From: David Brodbeck <DavidB@...l.interclean.com>
To: bugtraq@...urityfocus.com
Subject: RE: Is predictable spam filtering a vulnerability?

> -----Original Message-----
> From: PSE-L@...l.professional.org [mailto:PSE-L@...l.professional.org]

> Many sites employ SpamAssassin and the like to simply FLAG 
> messages and  pass them along to the intended recipient, who can then 
> employ their own  filter process within their email client

This is what I do.  Spam is tagged by a statistical filter, then tagged
messages are filtered into a "Junk Mail" folder by the user's email client.

In a corporate environment, where silently dropping mail from a customer is
totally unacceptable, this is a good compromise.  The user can skim their
junk mail folder now and then and pick out anything that looks like it's
important.  (I do this about once a day; only takes a few seconds.  A
non-spam message in a folder full of spam tends to be surprisingly obvious.)

> Of course, what do I know?  Up till now, I assumed 
> intelligent folk could 
> manage to send a reply to a listserv without also sending an 
> unnecessary 
> carbon to the original message poster, and if not, at least courteous 
> people would pay attention to the sigline making such a request...

If I did this earlier, I'm sorry.  I correspond with a lot of people who
prefer to get carbon copies of list replies, especially on moderated lists.
I'm also not in the habit of reading signatures because they tend to be a
waste of time.  After seeing several dozen with bogus disclaimers and the
like in them you lose interest...

> John Fitzgibbon wrote:
> >Archiving the dropped mail *and* terminating with a 5xx would be a much 
> >better approach.

To me that seems *totally* broken.  A 5xx response means you didn't deliver
the mail, and the failure was permanent.  Terminating with a 5xx and then
delivering the mail somewhere isn't kosher; in fact, it's the worst of both
worlds.  You've still accepted the spam, *and* you've potentially created a
DSN.