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Re: Everyone Greylists Except Honeypots ... So Let's Not Spam Honeypots!

2007-12-06 01:57:35

On Dec 5, 2007, at 6:51 PM, John C Klensin wrote:

This type of reasoning is exactly the reason why some of us are skeptical about greylisting and any other technique that works well only if it is used by sufficiently few people. If it starts being used enough, the spammers have the incentive to figure out how to simulate the behavior that gets past the traps and then, sooner or later, it isn't worth bothering with. The skepticism leads some of us to wander away from conversations about how wonderfully effective the technique while muttering "arms race". Others wander off in a slightly different directions muttering "making the bad guys smarter is really not a good strategy"

At least the first of those sources of muttering noises does not suggest that you shouldn't use a method that works for you as long as it does work for you (others might disagree about that). It does mean, I think, that you should be somewhat careful about praising the method to others or assuming that it will last forever. And then there is the part I worry about most, which is that we will make basic changes to the email protocols in order to make things work better, for a short time, for these relatively short-life- expectancy techniques.

SMTP's inability to reliably identify where a message originated has caused inordinate reliance on content filtering. While at first, content filtering had been fairly effective, this in turn has caused spammers to improve their obfuscation techniques at a rate that has become impractical for receivers to match with resources.

For each direct source of spam, there are 4 sources of spam emerging from tens of millions of MTAs as DSNs. The abuse of DSNs is seriously eroding email's integrity.

Few MTAs can operate and accept message for all recipients. The inability for MTAs to handle all possible traffic exposes valid recipients to being discovered.

Providers of domain names, IP addresses, or certificates have a conflict of interest, and are unable to prevent access to spammers.

SMTP can not even mandate the use of an MX record to avoid searching for policy records.

Reputation assessments of the last hop IP address is causing spammers to merge their traffic with other domains. Often this merging is accomplished through compromised residential systems. The doubling rate is at six months, quickly making last hop reputation assessments less meaningful.

While DKIM attempts to provide essential transport information, it is also prone to replay abuse and employs public key cryptography where sign-once / send-many gives transmitters a resource advantage.

Grey-listing does not afford any long term strategy. However, the use of temp errors can help avoid a complete denial of service as a triage strategy for limited receiver resources. Reputation is then used to establish priority. Processing undesired messages can exceed 99% at very high volumes. This is not how the Internet should work. A basic change to SMTP is needed to shift the burden toward the transmitter. Greylisting increases the number of transactions per message, so ultimately, this is headed in the wrong direction.

The TBR reference exchange can be done within a single transaction. The transmitter is required to hold messages until the receiver is ready. With a high level of source granularity, message origination reputation should be able match the transmitter's level of abuse and not breed super spam. References can be retained for a period of time, where abuse pattern can be detected and used to silently expunge abusive sources.