I just found out about this and signed up. It's called Nomorobo.com. According to others, this looks legit but feel free to google them and see if you can find any objective reviews. It's a free service to individuals. What I've read is that they intend to make money by charging business call centers.

The way it works is you sign up with an email address. You can use a bogus name and throwaway email. You also have to give them your phone number.

Your phone number has to have the simultaneous ring feature because the way it works is when a call comes in, they check the caller id. If it is a known robocaller, they pick up and then hang up. You only hear one ring.

In my case, my VOIP company wasn't listed. So I kept trying landline companies until I found one that worked. I think it was Optimum. When I got the email invite that let me setup my number I put it in and everything worked. They don't check who the carrier actually is.

My VOIP line also lets me block 800 numbers and numbers that block their caller id info. Nomorobo doesn't do this so I'm assuming the call will be blocked before it even gets to them in that case, but it will be interesting to see how that works.

If you try it, please report back with your story. I'll try to do the same.