On Fri, 25 Feb 2005, Matthew Newton wrote:
> On Fri, Feb 25, 2005 at 07:56:53AM -0800, Marc Perkel wrote:
> > If I want to put an initial 2 second delay in the initial creeting that
> > is sent before the user sends HELO - where would I put it? Trying to
> > trap spammers who send data two quickly without waiting for the proper
> > server responses.
>
> Interesting idea...
It works fairly well, catching about 10% of junk. We add a conditional
delay both before the inital banner and before the response to HELO. We
don't bother with extra delays after RCPT because RCPT is not a
synchronization point. We could perhaps add a delay in the predata ACL
which is the only remaining synchronization point where we don't impose a
penalty (though the various checks in the RCPT ACLs may be enough by
themselves). See section 3.7 of my paper for details:
http://www.cus.cam.ac.uk/~fanf2/hermes/doc/talks/2005-02-eximconf/paper.pdf
Tony.
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