> […]and they claim a false positive rate of just 0.35 per cent.
> (Since they write that 80,000 domains are registered each day, that's still around 250 sites a day unfairly tagged as evil, so PREDATOR still needs some refinement on that score).
The false positive rate is the proportion of sites tagged as fraudulent that shouldn't be. Not the proportion of all registrations. So it will be fewer than 250 falsely tagged sites. The paper does not seem (on a quick scan through) to suggest what proportion of registrations are fraudulent, but that 0.35% should be applied to that number not the total number of registrations.