Sources: the US has probed whether the products of China's Bitmain, which sells most of the world's Bitcoin-mining machines, pose risks of espionage or sabotage (Bloomberg)
https://www.bloomberg.com/news/articles/2025-11-21/chinese-manufacturer-bitmain-faces-us-security-review
http://www.techmeme.com/251121/p19#a251121p19