Multiplier for ipv4 address

[juliangruber]

IPv4 addresses are used as a scarce resource in the SPARK system.

When people only have an IPv6 address, we need to allow them to participate too, and map their address to an IPv4 address. This is currently done by Cloudflare automatically. It however creates an attack vector: Depending on Cloudflare's translation logic, it can be easy to get into a new IPv4 subnet through cycling IPv6 addresses.

Therefore, we propose to add a multiplier which rewards participants with IPv4 addresses higher. This improves the quality of our fraud detection, while still allowing anyone to participate. Unfortunately, this will reward innocent participants with just an IPv6 address lower.

[bajtos]

We can also add a penalty for IP addresses known to be assigned to datacenters, VPNs, open proxies and Tor exit nodes.

• https://github.com/X4BNet/lists_vpn