[SURBL-Discuss] RFC: SURBL inclusion policy

Ryan Thompson ryan at sasknow.com
Tue Sep 28 02:50:39 CEST 2004


Jeff Chan wrote to SURBL Discuss:

> So there is a point of diminishing returns in going with
> the older domains.  There is also perhaps an increasing
> chance of FPs with older domains.
>
> (I didn't graph the above, but the numbers look like a
> nice exponential decay....)

I have graphed similar numbers, but I don't have the results handy. It's
more like a normal distribution ("bell curve"), with the mean at 0 days
(actually slightly greater than zero, but that's a relatively constant
skew due to lag between registration time and spam delivery/processing).
GetURI uses a modified version of the normal distribution as part of its
heuristic. The other parts of GetURI's heuristic are pretty much all
additive, but I found that, statistically, domain age is good enough to
be multiplicative, and it'll *reduce* rankings for domains that have
been registered for a long time. It's so nice when math actually works.
:-)

- Ryan

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   Ryan Thompson <ryan at sasknow.com>

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