Spam Challenge-Response system

Michael Torrie torriem at gmail.com
Thu Apr 9 14:44:19 MDT 2009


Jessie Morris wrote:
> Postgrey was almost exactly what I was looking for. :) With Postgrey it's 
> almost completely automatic.
> 
> For anybody else looking for this kind of system, here's a pretty good link 
> talking about how to do it.
> 
> http://www.roedie.nl/wiki/index.php/Spam_Filtering_With_Postfix

Greylisting has worked very well for me.  In fact I get so few spam
message through that I can't even train dspam.

I have noticed, though, that over the last year or two more and more
spam bots are calling back and delivering their spam.  Maybe we need to
combine greylisting with some kind of tarpit idea.  Where we hold onto
their connection for 30-60 seconds before saying, "try back later."
That just might raise the cost for spammers just a little bit.  A
never-ending arms race.   That's for sure.



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