This is a work in progress. I'll update it with more info as soon as I get it. If you have more info, you can tell me at @mola_io, at the comments section or at email@example.com.
Vodafone Spain is deploying a web blocking system dubbed Castor. This is the first time that a Spanish ISP has taken the web blocking beyond the DNS level: they're performing large-scale Man-in-the-Middle attacks, intercepting HTTP requests to some website's IPs and serving an HTML redirect to their blocking system instead.