Hi, At [Upollo](1) we do a lot for detecting dodgy signups and helping users to convert. IP lists are a part of what we use and we are planning on making our IP API's public in the near future.

We find IP lists alone dont really cut it though. Its easy for someone to just tether to their phone to signup.

If your interested we would love to chat :)

[1] https://upollo.ai