Re: Hardening lists against spam attacks

[Toto <toto@sk.sympatico.ca>]

This is the first posting I have seen (someone unSCUMscribed me a
few days ago) which addresses the need for having defences in
place against spamming attacks.

  The fact is, the InterNet is a global neighborhood, and everyone
will be affected by the security or non-security of their neighbors.
Since the Web is currently seen as the new 'gold rush', every Tom,
Dick and Harry who wants to capitalize on it will be putting up
web sites, with their concern being focused much more on increasing 
their piece of the pie, than on being good neighbors.
  So sports lists are going to make it easy-as-pie for 10,000 Laker's
fans named Bubba to subscribe to their list and, as a result, make it
also as easy-as-pie for people to take advantage of their come-one-
come-all policy in order to engage in the sport of spamming. 

  While there are many good list operators who take reasonable
precautions against abuse of their system, they are often still
left open to abuse coming from the system of less concerned
list operators.
  It would seem to me that part of the solution would be to have
in place a monitoring system which would reflect a sudden increase
in email coming in from new (or current) sources.  Then the source
of any excessive increase could be put on 'hold' until the system
operator has a chance to check on the validity of the reason behind
the sudden increase.
  (20 messages from Bubba is an inconvenience, but 500 messages
is a royal pain-in-the-ass)

  As for 'mailbots', I think that any solutions to the potential
abuse will only be a 'stopping action', at best.
  My view is that the machines are starting to make their play
towards taking over, and that we will eventually be doomed to be
their slaves, and not the other way around.
 
Toto
Bill Frantz wrote:
> 
> The Christmas attack against this list shows the need to develop lists
> which are resistant to attacks.  If cyberspace is to become the town square
> of the next century, we need to be able to discourage brown shirts attacks
> on political gatherings.  If lists are to be a major part of the political
> life of the community, then they must be resistant to attacks from
> knowledgeable, well financed attackers, not just the shits who were the
> most recent perps.
> 
> There are several principles which should be observed:
> 
> (1) Since attacks are based on sending to the list, receiving the list
> should remain substantially unchanged.
> 
> (2) Spam attacks should be throttled at the source, so they do not act as a
> denial of service attack on the list server.
> 
> Here is a sketch of a protocol which attempts to achieve these goals:
> 
> (1) All messages sent to the list must be encrypted with the list's public
> key.  This requirement is primarily to protect the posting token (see
> below).  However, it alone will probably reduce the problem.  Certainly it
> will eliminate the effectiveness of the "subscribe the list to some other
> list" attacks.
> 
> (2) In order to post to the list, the poster must have a valid posting
> token.  These tokens are available, in limited number, anonymously.  Tokens
> remain valid unless canceled for abuse.  However, if too many posts are
> received with a given token, TCP performance on sockets using that token
> may become arbitrarily slow (or the circuit may be dropped).
> 
> (3) In order to limit the number of posting tokens, the list server will
> only issue a few per day.  The lucky few who get them, everyone who asks
> under normal circumstances, may be determined by an algorithm designed to
> limit token collection by future attackers.  (This area is where this
> proposal needs work!)
> 
> -------------------------------------------------------------------------> Bill Frantz       | Client in California, POP3 | Periwinkle -- Consulting
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