07.02.2017, 09:22
A reverse DNS lookup on an IP will end with the domain of the provider. In my case it will end with access.telenet.be. If the user is using a VPN, the IP will be that of the VPN so the lookup will lead back the VPN provider. If the IP can't be resolved or if it returns something like cloudflare.com then the request is almost certainly coming from a datacenter rather than the user's home.