Milter-greylist

Oliver Fromme <olli@...> wrote:

> I think a better approach (i.e. much faster and more
> reliable) would be to create a public database of such
> images.  Spammers aren't generating new images for every
> single mail, so that should be feasible.

But it's extremely easy for the spammer to generate a new image each
time, with a few changing pixels. That costs nearly nothing.

I haven't checked, but I would not be surprised if it was not already
the case.

OCR is time-consuming, but it can be spread on many machines, should you
need it. And in order to avoid DoS, you can decide that images
containing GIF are second-class citizen and process them slower than
regular mail. It's extremely easy to do: you only have to nice the OCR
computing.


-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu@...