Hola VPN is a malicious browser addon which hijacks the user PC and uses it as an exit node for other users of the VPN. It is currently used by +5M users who have no idea their own PC and IP are used by other users for all kind of criminal activities.
I have myself tested Hola VPN in a sandbox and browsed my site, then I checked the server logs and the two IPs I was given by the VPN are in US residential areas.
This proxy network is unblockable AFAIK since it uses millions of regular users PC in residential areas.
I have noticed that when doing a DNS scan with the Hola VPN, it returns google open DNS. Maybe cloudflare could use this to detect and block this VPN ? Of course it would require some tweaks to make sure google legitimate crawlers don’t get blocked as well.