Ned Freed wrote:
>> Spam filtering is sort of like chemotherapy, the difference between
the good and the bad is pretty small, and the trick is to find
measures that will kill the disease without killing the patient. It's
entirely a matter of statistics, not fundamental design.
And sort of not like it at all. For one thing, the mutation rate in the spam
world is much higher. And that brings us to the real issue here: Whether or not
a given technique, which was very effective indeed at one point, is effective
enough now to continue using.
At base, this requires distinguishing between techniques that are heuristics,
and therefore fickle, versus techniques that can be stable over the long term.
The former are used to detect bad actors. The latter can apply for handling
The bad actors are indeed bright, well organized, aggressive and very, very
adaptable. Any use of heuristics must therefore be extremely agile. The
diligence and expertise this requires is onerous. Typically, only the largest
services can afford to do this in-house.
By contrast, a trust overlay, based on prior assessment of good actors, ought to
be much lower overhead and much more stable. However we have less experience
with this side of the equation.
This defense definitely was very effective once upon a time, but the world has
Nor does continuing to use a technique that has outlived it's usefulness.
And in the specific case of the IETF, where we want to encourage people to use
our servers to experiment with IPv6 and where there are bound to be a lot of
PTR record issues, I think an absolute block on the basis of no PTR record is
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