Spam Challenge-Response system

Andy Bradford amb-plugg at bradfords.org
Fri Apr 10 12:10:38 MDT 2009


Thus said Jessie Morris on Thu, 09 Apr 2009 12:35:45 MDT:

> I was wondering if there was any  way that I could make my mail system
> respond to  emails received  with a  link that  says something  to the
> effect of,  "If you're a human,  click here to be  allowed." I've done
> some  searching on  Google, and  haven't found  a really  good system.
> Ideas?

TMDA and  qconfirm both  do this.  I used  to use  TMDA but  switched to
qconfirm (at least for inbound checking).

One other nifty tool you might consider:

http://peff.net/sendok/

I  believe TMDA  also  has  the ability  to  generate timestamped  email
addresses.

Now, if you do opt to use an MUA level C/R system like qconfirm or TMDA,
be aware that there are side  effects (some of them positive). You might
stop getting  emails from non-technical  people who can't read  a bounce
message that  says ``If  you are  not a spammer  please respond  to this
email.'' :-)  I also noticed a  drop in emails from  unknown people that
just happen to reply-all in response to forwarded junk mail from friends
and family.

Also be aware that these kinds of C/R systems can be vectors for attacks.

Andy
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