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Re: PS -- Re: Restricting the list

1996-02-06 11:10:07
To pre-empt an obvious objection:  My guess is that very few people are
both technologically sophisticated enough to know how to change their
Email address and culturally unsophisticated enough to use that
knowledge to inappropriately spam mailing lists.  But there will
undoubtedly be a few.  -- NB

As a long-time subscriber to the FV list, I'm very familiar with the problems
there that Nathaniel has set out to address. And I agree that in this limited
case a bozo list can be an effective tool.

Unfortunately this approach is completely worthless when it comes to the sort
of spamming that started this discussion. Nathaniel may be correct in his
assessment that most people lack either the sophisitication or attitude
necessary to change email addresses. Nevertheless, "most people" is known not
to apply to the typical originator of this sort of spam. We have ample evidence
that this is the case. Usually origin addresses are bogus and are chosen to
make a point. The nude videoconferencing spam that started this discussion was
an example of this. The ongoing magazine subscription spam that keeps coming
back is also an example, and so is the learn-while-you-sleep spam. Some of
these things are sufficiently sophisticated that they use different addresses
on each list they post to.

There is actually a book that describes how to spam and I'm told it
specifically recommends using different addresses each time a spam is sent out.

I must also point out that the state of the art in spam prevention is already
far past this point. It is worthwhile to review the various methods that
are available:

0. Use news and not mail. News has a key feature email lacks: Messages can be
   recalled after being sent. Unfortunately settting up newsgroups is much
   more involved than setting up mailing lists, so much so that it is
   impractical to talk about converting most mailing lists to news.

1. I've already pointed out that filtering on specific origin addresses is
   totally ineffective.

2. Filtering duplicate postings to multiple, unrelated lists is somewhat
   successful now, but there are clear indications that spammers have already
   figured this out and are taking steps to post different variants to each
   list. Building software to generate such variants is technology that is well
   understood -- I recall a program on a system I used back in 1978 that wrote
   random dirty poetry, and it was old when I first encountered it -- and it's
   only a matter of time before use of this technology becomes routine. 

   Furthermore, the filters used to implement this sort of thing often misfire
   and block legitimate postings: I've had more than one posting that quoted
   from previous postings rejected by some LISTSERV variant, and I generally
   don't bother to repost such things, which I'm conceited enough to think is
   not to the advantage of the list.

3. Restricting lists to postings from list members is very effective at the
   present time, but it is also hugely inconvenient to list participants. I've
   already stated my firm policy in this area: I absolutely refuse to cater to
   such software. And if this approach becomes widespread it can easily be
   overcome by spammers: All they have to do is set up a robot that subscribes
   to lists and captures one or more addresses of people who do manage to post.
   I figure I could write the software to do this in an afternoon, and it is
   silly to suppose that the spammers would be unable do something similar.
   Heck, if such restriction become widespread someone probably could write
   the software to do this and sell the results it generates to the spammers!

4. Scanning postings for inappropriate material is an approach that looks
   attractive but is very difficult to implement in practice. You may be able
   to catch offsensive text, but I'll bet there wasn't anything in the
   magazine subscription spam that you could easily latch onto. And what are
   you going to do about someone who, now that MIME-capable readers are
   getting to be pretty common, posts a GIF image? Scan the image? The
   technology in this area isn't up to the challenge, I'm afraid. And an
   approach of blocking all GIFs or whatever won't work since people are
   starting to use them as signature files and so on.

5. Inserting a delay in the list that offers a shot at manual intervention
   and deletion of inappropriate material is somewhat effective. But spammers
   tend to come out at night, when people able to scan such messages are
   in short supply, and inserting delays long enough to insure that reviewers
   are available can be very inconvenient.

6. Hybrid approaches employing one or more of these ideas, coupled with partial
   moderation (where instead of rejecting suspect messages outright they are
   sent to a moderator for review) is about the best mechanism we have at this
   time. But anyone implementing this should take note of a key point: The
   specific automatic review mechanism they decide on should not be revealed
   publicly. The minute you publish the details of the specific approach you
   use you have provided the enemy with the means to get around your

   The problem with this approach, of course, is that list managers have to
   acquire the sophistication to set up such things.

This last point in the killer when it comes to commercial software. A single,
standardized list filter simply won't cut it. As such, the approach we've taken
in our PMDF product is to provide the tools necessary implement a wide variety
of list filters. Sites can then build the filters they want from the available
tools. I don't know (and don't want to know) the specific mechanisms people
have implemented using the tools we provide. This requires both substantial
management skills and competent technical support from the vendor, but it is
the best we've been able to come up with.

The long-term prognosis, however, is gloomy: There is no single universally
effective long-term solution to these problems other than full moderation of
all lists at all times. And the more half-assed measures we employ the more we
inconvenience list participants while not managing to inconvenience the
spammers significantly.

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