> -----Original Message----- > From: Clifton Royston [mailto:[EMAIL PROTECTED] > Sent: Tuesday, 26 July 2005 6:49 a.m. > To: Stuart Johnston > Cc: [EMAIL PROTECTED]; amavis-user@lists.sourceforge.net > Subject: Re: [AMaViS-user] FINAL DECISION: Will our machine handle it > > > I thought that rejecting non-existent users at SMTP time > was considered > > a bad idea because now the spammer knows that any messages that are > > accepted are valid email addresses. > > I believe this was always largely a myth. While there was evidence > of a few spammers who actually winnowed out their lists, most do not.
Agreed. > This is pretty clear proof that the vast majority of spammers never > winnow their address lists. If you accept all addresses, you will just > end up with more junk to deal with. Exactly, and it opens you to backscatter attacks. For those interested, first part of my presentation shows how bounce attacks work and why you should block them (it's not the best thing in the PDF, if someone is interested let me know and I can send you the PPT). Spammers today usually don't care if the address is existent or not - they have hunderds, if not thousands, of bot machines which will just spit out spam to any address, including those found on the local machine. In order for a spammer to detect that the address is not in use (ie. it's rejected), a spammer has to: 1) either write a program which will deliver e-mail directly to your server so he can parse replies; or 2) monitor bounces to the e-mail address they put in the From: field. As we can see, 2) doesn't work at all because spammers won't use legitimate From: addresses; besides that no matter what they did, their inbox would probably be flooded in a matter of seconds. 1) can work, but I'm pretty sure they are still in "fire & forget" mode. Cheers, Bojan ------------------------------------------------------- SF.Net email is sponsored by: Discover Easy Linux Migration Strategies from IBM. Find simple to follow Roadmaps, straightforward articles, informative Webcasts and more! Get everything you need to get up to speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click _______________________________________________ AMaViS-user mailing list AMaViS-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/amavis-user AMaViS-FAQ:http://www.amavis.org/amavis-faq.php3 AMaViS-HowTos:http://www.amavis.org/howto/
