I'm reading between the lines here based on scanty hints (based on the remarkable uniformity of spammer's arguments that they are doing a good thing), because I'm not intimately familiar with the world of spammers, but the biggest spammers seem to talk to each other fairly regularly. If one of them has figured out how to do it, rest assured that it is not long before they all know how.
There is a definately cycle to all of these things:
- A new technique is developed.
- Early adopters use it, and acheive amazing fantastic spam reduction rates.
- It starts to increase in popularity.
- The critical turning point is when a major ISP uses it as part of its spam filters, keeping the spam away from the few people who would actually respond to it.
- The spammers counter-attack and get around the filter, and rapidly spread how to do this amongst themselves.
- The resulting endless arms race, where taken over time only a fraction of the spam is blocked, finally ends when the spam fighters give up on the technique and go to a new one.
In light of this further analysis, I'll refine my challenge. Three months after a major ISP affecting hundreds of thousands (or more) of mailboxes starts using Bayesian filtering server-side, I predict that the filters will be largely useless. Takers?