Defensio seems to be purposely vague about what goes on “under the hood”. Why?
It’s true, we’re intentionally unspecific about the underlying technologies and methodologies we’re using to fight spam. It’s not that we’re uncomfortable with disclosure, nor that we lack confidence in the strength of our filter; but rather, we believe it’s in our collective interests to keep the spammers guessing as much as possible (they are, after all, reading this site along side good people like yourself).
