(Co-Producer - Vice Media)

In 2014, before Ethereum and altcoin mania, before ICOs and concerns about Tether and Facebook's Libra, Motherboard gained access to a massive and secretive Bitcoin mine housed within a repurposed factory in the Liaoning Province in rural northeast China.

This is the infrastructure that keeps the digital currency’s decentralized network up and running, and its operators were profiting big time.

The mine we visited was just one of six sites owned by a secretive group of four people, part of a colossal mining operation that, as of our visit, cumulatively generated 4,050 bitcoins a month, equivalent to a monthly gross of $1.5 million as of 2015. Since then, the cryptocurrency mining world has become even more extreme.