Re: reject vs. delete
Jared Johnson wrote: Hi, The product I've been working with allows th user to set Rejection and Deletion thresholds, at which a message identified as spam will be rejected with 550 - Message is Spam etc., or accepted with 250 OK but dropped on the floor, respectively. Historically it has been believed that if we have a high enough confidence that a message is spam, it is adventageous to pretend we have accepted the message in order to avoid allowing spammers to know whether their methods are working. I have not verified anywhere that this practice really does have a negative impact on spammers. This would especially be invalidated if most of the rest of the spam filtering world does not make use of 'delete' and simply issues rejections -- in that case, if the spammers don't get the information from me, they'll get it from the next guy. I do know that having a delete threshold occasionally causes false positives to go undetected by end users. That is a bit of a disadvantage. The suggestion has also been raised that claiming to accept spam rather than rejecting it might invite spammers to send more spam your way. Does anyone have any knowledge or opinions on these matters? Does pretending to accept a message contribute to the fight against spam in some way? Or does it invite more spam? Is it worth it? I don't think you should care, because different spammers act differently, and they can also change their behaviour. here are few points. - if the user discards mail, it's the user problem. (no RFC can force a user to read any mail). - to avoid backscatter, you can only reject during the smtp transaction on the edge of your network (when receiving mail from strangers. if you receive mail from a relay of yours, it's too late) - rejecting based on the envelope (before reciving DATA) is generally better since you don't have to receive the message. if you read the message, then reject is not necessarily better than discard/quarantine. - some clients will try to resend if you reject. here is an example: May 24 00:02:42 victim postfix/smtpd[24555]: NOQUEUE: reject: RCPT from unknown[88.244.89.158]: 554 5.7.1 [88.244.89.158]: Helo command rejected: Literal IP Helo is no more accepted because of spam; from=[EMAIL PROTECTED] to=[EMAIL PROTECTED] proto=ESMTP helo=[88.244.89.158] May 24 00:03:22 vicim postfix/smtpd[24555]: NOQUEUE: reject: RCPT from unknown[88.244.89.158]: 554 5.7.1 [88.244.89.158]: Helo commmand rejected: Literal IP Helo is no more accepted because of spam; from=[EMAIL PROTECTED] to=[EMAIL PROTECTED] proto=ESMTP helo=[88.244.89.158] ... I don't know whether they retry if the first spam was accepted. here, they retried the same recipient by changing the sender address. sometimes, they change the helo name. sometimes they retry with the same envelope...etc. - if you discard, you must make sure to never discard legitimate mail. - if unsure, you can provide a quarantine (Junk folder being one example). however, a quarantine full of junk is generally equivalent to discard (except maybe for the ability to save an FP if the user is made aware of it via other means).
reject vs. delete
Hi, The product I've been working with allows th user to set Rejection and Deletion thresholds, at which a message identified as spam will be rejected with 550 - Message is Spam etc., or accepted with 250 OK but dropped on the floor, respectively. Historically it has been believed that if we have a high enough confidence that a message is spam, it is adventageous to pretend we have accepted the message in order to avoid allowing spammers to know whether their methods are working. I have not verified anywhere that this practice really does have a negative impact on spammers. This would especially be invalidated if most of the rest of the spam filtering world does not make use of 'delete' and simply issues rejections -- in that case, if the spammers don't get the information from me, they'll get it from the next guy. I do know that having a delete threshold occasionally causes false positives to go undetected by end users. That is a bit of a disadvantage. The suggestion has also been raised that claiming to accept spam rather than rejecting it might invite spammers to send more spam your way. Does anyone have any knowledge or opinions on these matters? Does pretending to accept a message contribute to the fight against spam in some way? Or does it invite more spam? Is it worth it? Jared Johnson Software Developer and Support Engineer Network Management Group, Inc. 620-664-6000 x118 -- Inbound and outbound email scanned for spam and viruses by the DoubleCheck Email Manager: http://www.doublecheckemail.com
Re: reject vs. delete
Does anyone have any knowledge or opinions on these matters? Does pretending to accept a message contribute to the fight against spam in some way? Or does it invite more spam? Is it worth it? I accept all spam, and then (for higher spamminess automatically) report them thru SpamCop. If I would not report them, I would reject them at once. No report, no idea to accept spam. It depends. For all spam I report, only one or two ISP:s send a message back confirming a kill. So I have no idea if reporting via SpamCop helps in the fight or not.. But that's what I do.
Re: reject vs. delete
On Fri, May 23, 2008 at 3:00 PM, Jared Johnson [EMAIL PROTECTED] wrote: Hi, The product I've been working with allows th user to set Rejection and Deletion thresholds, at which a message identified as spam will be rejected with 550 - Message is Spam etc., or accepted with 250 OK but dropped on the floor, respectively. Historically it has been believed that if we have a high enough confidence that a message is spam, it is adventageous to pretend we have accepted the message in order to avoid allowing spammers to know whether their methods are working. I have not verified anywhere that this practice really does have a negative impact on spammers. This would especially be invalidated if most of the rest of the spam filtering world does not make use of 'delete' and simply issues rejections -- in that case, if the spammers don't get the information from me, they'll get it from the next guy. I do know that having a delete threshold occasionally causes false positives to go undetected by end users. That is a bit of a disadvantage. The suggestion has also been raised that claiming to accept spam rather than rejecting it might invite spammers to send more spam your way. Does anyone have any knowledge or opinions on these matters? Does pretending to accept a message contribute to the fight against spam in some way? Or does it invite more spam? Is it worth it? I prefer to follow the spirit if not the letter of the RFCs. If I am not going to take responsibility for a message, I reject it. I do accept some things and quarantine them rather than put them into a user's mailbox, but I never just throw anything away after saying I will deliver it. There are plenty of sites that do silently throw away mail, and plenty that will reject. unless you are a *really* big site I really don't think spammers are going to care what you do, if they notice at all. I'd worry more about the legitimate users and what happens to their mail in a false positive situation. -Aaron Jared Johnson Software Developer and Support Engineer Network Management Group, Inc. 620-664-6000 x118 -- Inbound and outbound email scanned for spam and viruses by the DoubleCheck Email Manager: http://www.doublecheckemail.com
