Bayes Poisoning? Spam with negative BAYES Scores - ahhhh

Mark Nienberg mark at TIPPINGMAR.COM
Wed Dec 24 17:55:33 GMT 2003

I finally decided to modify the scores for Bayes probabilities less than 50%, so Bayes
will not reduce overall spam scores anymore.  If Bayes thinks the message is spam,
it will increase the score as always.  If it thinks it is not spam, there will be no
significant reduction in score.  Here is what I put in spam.assassin.prefs.conf.

score BAYES_00 0 0 -0.05 -0.05
score BAYES_01 0 0 -0.04 -0.04
score BAYES_10 0 0 -0.03 -0.03
score BAYES_20 0 0 -0.02 -0.02
score BAYES_30 0 0 -0.01 -0.01

Most of the spam where I see Bayes erroneously giving low probabilities consists of
a single html image (with the real message) and then a bunch of random dictionary
words, probably intended to trigger a negative Bayes score.  I don't think training
Bayes on these spam messages is going to help any.  Won't it just tokenize the
random dictionary words and begin to associate them with spam?


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