What scripts are capable of bypassing CloudFlare/proxy services and how do they do it? Do they look for old DNS records that leak their Origin IP or something like that?
Spin up a hefty AWS instance and connect to every single IPv4 IP while sending a HTTP get request on successful connects with a Host matching that of the domain. There are only 4 billion IPs. Look for successful code 200's with the same headers and content as the original website. Easier said than done though.
Btw, this attack can be prevented if you run a drop-all firewall and only whitelist the IPs listed here: https://www.cloudflare.com/ips/