Supposedly introduced as a crude DRM to control illegal equipment, the company forgot to tell anyone about it, and even ignored a user who reported it last fall. One of the Bitcoin Core developers claims that if such command would ever be sent, it could potentially brick the customer's device for good.
Bitmain is today's most popular seller of Bitcoin mining hardware, and its products account for 70% of the entire Bitcoin mining market. If someone hijack's the domain where this backdoor reports, he could be in the position to shut down Bitcoin mining operations all over the world, which are nothing more than the computations that verify Bitcoin transactions, effectively shutting down the entire Bitcoin ecosystem. Fortunately, there's a way to mitigate the backdoor's actions using local hosts files.