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Economics of SPAM [Was: Micorsoft's Sender ID Authentication......?]
- From: Andre Oppermann
- Date: Fri Jun 10 12:40:30 2005
On Thu, 09 Jun 2005 17:40:55 PDT, Matt Ghali said:
So you see, the reputation has nothing to do with your mom, and
everything to do with the controlling entity, her ISP. Which makes
the whole address-based sender reputation scheme almost workable, if
you ignore the scaling issues.
That's suspiciously close to "Ralph Nader or Ross Perot could have been elected
President, if you ignore the scaling issues". :)
Other than that, what Matt said is correct - the problem is that legitimate
mail can come from literally millions of places whose reputation we have no
Everyone in the SPAMwar has to be aware that SPAM can't be stopped until
its transaction costs approach that of the cheapest other advertising
method. That can be snailmail spam, telephone terror^Wmarketing, whatever,
you name it.
SPAMmers will do whatever is economically feasible to send their SPAM.
If this includes commanding zonbie armies they will. If it includes
hacking real mailserver with good reputation they will. If it includes
buying IP space they will. You have to manage to lower the reputation
of that host within a very short amount of time to increase the
transaction costs sufficiently for the spammer to make the effort
worthwhile. On the other hand you make the life for the hacked mail
server miserable. And if you let the reputation of a host bounce
back to fast spammers will use it by schedule. Spam for two hours
today and again in two days and again and again.
The current Internet email system is an open system because SMTP was
built that way. Note that there can't be any other 'rewrite' of SMTP
that fixes the SPAM problem and remains open at the same time. It follows
that all the chatter that SMTP is broken is false and misguided unless
you want a closed system controlled by one entitiy.
Everything that can be done to keep the SPAM problem in check (fixing is
impossible by definition):
1a) must be simple so that many million server administrators can understand it.
1b) must scale to millions of legitimate mail servers.
1c) must not break common functionality for users.
With high probability there is no one (complex) system fulfilling all of
these point at the same time. In all likelyhood it can only be achieved
by a combination of simple systems/mechanisms each tailored to deal with
a specific part of the problem. This kind of approach not only scales on
the deployment side but also on the time line. Spammers adopt and will
change strategy as they have done many times in the past.
The options we have are:
2a) forward DNS based information (reverse MX information).
2b) reverse DNS based information.
2e) cryptographic signatures.
Each of them can contribute to a different part of the problem and none of
them can fix the entire one. IETF MARID tried to stuff too many things into
one of the above systems and failed.
Each of them has its own unique advantages and disadvantages and tackles
the problem on a different layer and is under different administrative
Now create a specific (sub)problem description, select the approriate
option from above and specify a *simple* and easily understandable
mechanism to make use of it.
[Info: I'm one of the authors of qmail-ldap which is a large-scale
clustered mail server software used by ISPs as Speakeasy.net in the
US and India's Rediff among others]