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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: SMTP store and forward requires DSN for integrity
>>>>> "JP" == JP Velders <[email protected]> writes: JP> Right now dumb AV filtering is akin to a Smurf amplifier. Good analogy. I would extend it by pointing out that "dumb AV filtering" is actually only a part of the general backscatter problem. The existence of BATV isn't an excuse for mail system operators to ignore the backscatter problem any more than the existence of stateful firewalls is an excuse for people to run smurf amplifiers. Right now, unless you are a large provider or corporate, or unless your mail system is massively over-engineered, any spammer can, at any time, drown you in bounces (30 million SMTP transactions in response to one spam run has been observed in practice). 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. It is, in my view, the responsibility of every mail system operator to design and operate their systems in such a way as to minimize the impact of backscatter on innocent third parties. This is not to say that DSNs should not be sent (because that would indeed cause an integrity problem) but that they should be avoided. Forged virus backscatter is just one of the more trivial examples (trivial because much of it is caused by A/V systems that _know_ they should not be doing it); there are many other sources of backscatter that are not specific to viruses, most of which can easily be controlled by proper feedback to the SMTP server (e.g. accounts which go over quota and _stay_ that way should be set to reject traffic at SMTP time, so that they don't become continuous sources of backscatter). -- Andrew, Supernews http://www.supernews.com
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