Date: Wed, 26 Nov 1997 18:58:28 +0200 From: Mark Murray <mark@grondar.za> To: "Jordan K. Hubbard" <jkh@time.cdrom.com> Cc: Greg Lehey <grog@lemis.com>, "Jonathan M. Bresler" <jmb@FreeBSD.ORG>, chat@hub.freebsd.org Subject: Re: major push by spammers? Message-ID: <199711261658.SAA00331@greenpeace.grondar.za>
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"Jordan K. Hubbard" wrote: > > How are you recognizing the spammers? > > 2 ways: The first, if reverse DNS lookup fails, accounts for about 90% > of the rejects. When I first started doing this, I worried that > perhaps I was rejecting some legit emails so for the first couple of > weeks I'd do one day on, one day off. In 14 days worth of testing, I > got one "legitimate" message (though it was unanswerable due to said > misconfiguration, so I could have done without it :) and many many > hundreds of spams on the days that I had reverse DNS checking > disabled. Needless to say, I can't even imagine not having it on now. > > The second way, which accounts for that last 10%, is to reject > according to a ban list which is maintained by the folks at gulf.net > (to which we add our own local banlist). By far the mest method is Paul Vixies RBL (Realtime Blackhole List). See http://maps.vix.com/rbl/ - There are some sendmail rules that work really well. The cool thing is that DNS outages are failsafe. M -- Mark Murray Join the anti-SPAM movement: http://www.cauce.org
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