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Re: SMTP store and forward requires DSN for integrity

  • From: Micheal Patterson
  • Date: Sun Dec 11 05:55:36 2005




----- Original Message ----- From: "Douglas Otis" <dotis@mail-abuse.org>
To: "Andrew - Supernews" <andrew@supernews.net>
Cc: <nanog@merit.edu>
Sent: Saturday, December 10, 2005 3:54 PM
Subject: Re: SMTP store and forward requires DSN for integrity


On Sat, 2005-12-10 at 17:37 +0000, Andrew - Supernews wrote:

BATV doesn't help you if the problem is SMTP transaction volume, any
more than a firewall will help you cope with a saturated network link.
I agree with most of your statements. AV filters should be done within
the session when possible, etc.

Your statement regarding BATV is not correct however. There are two
ways BATV reduces SMTP transaction volume when dealing with forged
DSNs.

"... BATV reduces SMTP transaction volume when dealing with forged DSNs."

If malware detection systems would not generate a DSN to the originator upon detection in the first place, there would be no need to reduce those transactions as there would be no transactions to reduce. The solution, to me, seems so simple, I must be overlooking something or not comprehending fully what the issue truly is. I thought that the initial problem was with AV mechanisms sending out DSN's to incorrect sender addresses. Please, if I'm so far off base, would someone be so kind as to email me off list and clear this up for me?

Honestly Doug, you do realize that your reluctance to stop the problem at the source conveys to everyone on this list the impression that you're only trying to gain support for your proposal don't you?

Let's take the malware and av scanners out of the picture for a moment. There was a time, long ago, where malware didn't exist in the email network. At that time, when a message was undeliverable, a DSN was sent to the originator of the message. It happens. Typo's and such. No one complained. Why? Because legitimate email, in order to function requires a valid email address for both parties. Why would they falsify it if they wish to communicate?

Now, let's look at it as of "today".

If someone sends someone a virus, intentionally, it's main purpose is to get to as many systems as it possibly can, as fast as it can to allow the software to propagate before it's detected by AV software. Do you REALLY think that the initial sender wishes to be told that he sent a virus? Do you really believe he/she wishes to even be known or contacted by you in any way? Of course not. Then why do these systems still attempt to send these notices? Well after all logical reasoning has indicated that the sender is forged. The software of today has no way of knowing if the originating system is the actual system that's introduced it into the wild or a carrier. It has no way to validate the email address of the sender. Can BATV correct this? Possibly. But at what cost Doug? How much will it cost them to get the latest and greatest so that they can implement BATV? How much down time will they have to deal with to implement it? Multiply that by the millions of mta's around the globe. Now, you tell me Doug, which is easier for everyone to do? Upgrade/update their mta's around the world or have those few AV detection vendors recode their software? I don't know about you, but if what little information I've found on BATV is current, most folks will have to switch to Exim or NetQmail just to get it to work currently. There's a lot of postfix and sendmail networks out there that may not want to switch. What happens to them?

Mike P.





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