Hard problem i’m trying to solve..

There's companies out there that will let you upload a list of IP Addresses and the system will spit back out the names, address, email, phone number sometimes even their credit score, household income data, etc connected to those IP addresses.

It won't do the whole list of IP's. Most have a 40-60% match rate. meaning you'll only be able to get the IP owners info for around half of the list you upload.

Does anyone know how they do this?

If I had to guess i'd say they have access to some massive national database that has all the info and they some how cross reference the IP addresses with it to find matches but I haven't been able to find any info of possible data bases like that.

Let me know your thoughts.