Francesco Peeters schreef:
Ruud H.G. van Tol:
Stalling IP-nrs that are not in a cache with all the most recent
connecting IP-nrs, does also work well. Make newcomers wait for a few
seconds and give them a 4xx temporary error, and put their IP-nr in a
special temporary cache. If they don't come back withing a few hours,
forget about them. If they do come back, only then do all kind of
SMTP-checks possible, and add them to the IP-nr cache only if all OK.
Beware: aol and yahoo don't like 4xx, so again some whitelisting
will be necessary.
I *love* grey-listing
I would start calling it 'greylisting' when more dimensions are added;
at least using the triple {Sender, Recipient, SMTP client IP-nr}.
The system I described tests basic RFC-compliances (by not playing nice
itself, but only to newcomers). The 'few seconds' (make that about 60)
will filter out clients that can't wait. The 4xx-error will filter out
clients that won't return.
Of course it'll - unfortunately - only be a
matter of time before the zombie-worms will circumvent this by
retrying on 4xx errors! :-(
Will take ages; there are still plenty of servers left that accept any
connection.
--
Grtz, Ruud
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