[rescue] Spam (was: Perverse Question)

Phil Stracchino alaric at caerllewys.net
Sat Jun 7 13:51:54 CDT 2003

On Sat, Jun 07, 2003 at 11:19:33AM -0400, Patrick Giagnocavo +1.717.201.3366
> I guess this is going OT, but my opinion is that simply passing a law
> that forging email headers is illegal would pretty much fix what needs
> to be fixed.

I think that'll do about as much good as laws making murder, rape,
robbery and arson illegal, or (perhaps a better analogy) laws making it
illegal for criminals to possess firearms.  Just as criminals don't obey
laws, neither do spammers.

If you want to prevent header forging, you can't do it legislatively.
It's going to have to be a technological solution.  Something like this,

Suppose the applicable RFCs were to be modified to define a fixed set of
origin mailheaders which ALL mail must include, that set to include a
header which contains a public-key signature of the MD5 digest of the
remainder of the set of headers using the secret key of the originating
mailserver.  If AT ANY POINT during the message's transmission the
signed MD5 digest is not present, cannot be verified using the public
key of the server the mail purports to originate from, or does not match
the contents of the mandatory headers, then the mail is dropped and the
postmaster of that hop and the previous hop are notified.

I believe this would prevent forging of mail origin headers, but still
allow anonymous remailers such as Mixmaster to function since they
already strip out all origin information and re-originate messages. This
might to some extent shift a burden onto operators of anonymous
remailers to verify that mail they are remailing is not spam; however,
(a) with a relatively small number of remailers in operation, there
should be a fairly small number of "choke points" at which spam can be
extracted from the message stream via bayesian filtering, and (b) I
don't believe that the mode of operation of anonymous remailers (which,
to my knowledge, operate one-to-one rather than one-to-many) lends
itself relaying large amounts of spam.  If my understanding is correct,
each message from the spammer would have to be individually sent to the
anonymizer, rather than cc'd to hundreds or thousands of addresses.  I
believe this would make it infeasible for the spammers to operate.

Comments, anyone?

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