At 10:29 AM 6/20/2003 -0500, Evan Harris wrote:
Over the past few months, I've been working on a new method of blocking spam
that I've termed "Greylisting". From my testing it appears to be over 97%
effective.
It requires no changes to the infrastructure, is resistant to spammer
adaptation, and is very effective, yet very lightweight.
The paper outlining the method is at
http://projects.puremagic.com/greylisting/ and I have also posted an example
implementation for a Sendmail Milter written in perl.
Please look it over and try to poke holes in it, but I've worked pretty hard
to make it as bulletproof as possible.
The main point of this method seems to be:
--snip---
"The Greylisting method is very simple. It only looks at three pieces of
information (which we will refer to as a "triplet" from now on) about any
particular mail delivery attempt:
The IP address of the host attempting the delivery
The envelope sender address
The envelope recipient address
From this, we now have a unique triplet for identifying a mail
"relationship". With this data, we simply follow a basic rule, which is:
"If we have never seen this triplet before, then refuse this delivery and
any others that may come within a certain period of time with a temporary
failure. "
--snip---
This proposal has been discussed before by someone else (I forget who), and
is similar to the one used by TitanKey. The underlying assumption is that
spammers will not retry message delivery. This may very well change very
quickly. As I stated before, we need to look to developing a "consent
architecture" for spam control like the charter says.
Yakov
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