I don't think there is a technology that can do that. I think fraudulent calls are a subset of nuisance calls. I think they're all nuisance calls, whether or not they're legal.
We're paying a lot more attention, though, to the fraudulent calls, because they've been growing so much lately and the idea is that they hurt people more. Being disturbed on a Sunday morning is bad. Having your life savings stolen is a lot worse. I think that's the difference in the focus.