I own a service that might help you and with your use-case the free tier will probably last you a lifetime :) Check www.adscore.com - I use it for my other proj

I own a service that might help you and with your use-case the free tier will probably last you a lifetime :) Check www.adscore.com - I use it for my other projects for detection and prevention of payments with stolen credit cards with very decent results. It will also help you to block automated registrations. Any questions, drop an email to support at adscore.com and I will assist you.