Re: Bug#207300: tmda: Challenge-response is fundamentally broken
Karsten M. Self <kmself@ix.netcom.com> wrote:
[...]
> SpamAssassin achieves a false-positive rate (non-spam reported as spam)
> of 5% with a default threshold of 5. This can be dramatically improved
> using a whitelist, to ~98% in my experience. This is not the best
> performance of all filters, so makes a somewhat generous threshold.
> http://www.spamassassin.org/dist/rules/STATISTICS.txt
> http://freshmeat.net/articles/view/964/
> So a spam-reduction system user would at worst see a typical rate of 2%
> of spam to be manually disposed of.
[...]
You are mixing up percentages. "5% non-spam reported as spam" ... can
be ... improved to ~98% ...
I would not use a filter which would tag 98% of my regular mail as
spam.
Perhaps you wanted to write 2%? No, does not match either, because the
last sentence does not talk about false-positive at all, it talks
about false negatives, i.e. spam that was tagged as non-spam.
When I last checked my personal rate with spamassassin 2.55 with
default rules and no DNS lists or razor (but including a rather well
trained bayesian filter) and a default threshold of 5, I came up with
these numbers[1]:
* 0% false positives, i.e. ham sorted into the spam folder
* 10% of the spam was not recognized as such and I had to filter it
out by hand.
Of course the numbers depend a lot on the people you are communicating
with, if your partners used Lotus Notes and sended everything in html
you might get false positives with score 5.
A properly trained bogofilter will give better results but is not
as effective as site wide service an requires more work to keep it
properly trained.
cu andreas
[1] I am quite happy with these, I can live with ~10 spams per day in
my inbox.
--
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http://www.logic.univie.ac.at/~ametzler/debian/tin-snapshot/
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