Reasonable and unreasonable bulk mail

Gary Mills mills@cc.umanitoba.ca
Mon Mar 15 14:38:04 UTC 2010


On Sat, Mar 13, 2010 at 03:30:28AM +0000, Vernon Schryver wrote:
> > From: Gary Mills 
> 
> > don't expect to be bulk mail.  I realize that I could whitelist
> > checksums of empty message to alleviate that problem, but unless this
> > process is automated, I'd have to be doing it regularly.  We also
> > advise people to add some text to empty messages, but that seems like
> > a peculiar solution.  Is there anything else I can do other than
> > disabling the Fuz2 checksum?
> 
> I disagree with several assumptions there.
> One is that only the FUZ2 checksum catches what might be called empty
> messages.
> Another is that most such empty messages are wanted email instead
> of viruses, worms, phishing, trojan horses, and other kinds of spam.  

You are correct here.  I was only looking at messages that people had
whitelisted; they must have wanted them.  I don't know how many spam
messages they had not wanted and had not whitelisted.  This is part of
the problem, of course.  I still don't have a good prediction if what
will happen if I disable the Fuz2 checksum.

> Then there is the notion that filtering spam can be free in time,
> effort, and money.

Users may assume that.  I don't.

> If using the cron script /var/dcc/libexec/fetch-testmsg-whitelist in
> the DCC source to maintain a current copy of the iecc.com list of
> checksums of empty and test messages and contributing new checksums to
> John's list is too much trouble or if John's list is not suitable,
> then it sounds best to disable DCC checking for some or all of your users.

I have been using that whitelist file but downloading it manually.  My
copy is now a year old.  Oh look, the new copy I just downloaded is
the same except for white space!  It's true that I haven't been
contributing to it, but obviously nobody else has been doing that
either.

That highlights another part of the problem.  Checksums of empty
messages change regularly because e-mail senders change their MIME and
HTML goo, along with their advertizing footers.  I don't have a way to
detect empty messages.  Users can only whitelist them by sender; they
don't realize that they are empty.

> P.S. I think I've made some useful changes to that cron script since I
> released the years old version of the DCC software that you are using.

Thanks for maintaining stable interfaces.  A software upgrade is in my
plans.  So is retirement.  Which will win?

-- 
-Gary Mills-        -Unix Group-        -Computer and Network Services-



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