Domain Fronting’ can be used to mask censored services by hiding them within infrastructure provider’s vast network. The technique, known as “domain fronting,” can also be used for cybercrime and online espionage. In December 2016, encrypted messaging app Signal said it would use domain fronting to evade censorship. In mid-April, Google disabled the practice, and Amazon has now followed suit. In March 2017, suspected Russian hacking group dubbed APT29 used it to hack outbound connections.”]
Source: https://www.cuinfosecurity.com/amazon-google-block-trick-that-let-encrypted-chats-flow-a-10954