The F.B.I. said on Saturday that North Korea was responsible for the hacking attack on Binance this week, the first official acknowledgment of the regime’s role in the biggest crypto heist in history.

Poor, isolated and heavily sanctioned, North Korea is not a country you would expect to field an elite army of hackers capable of pulling off billion-dollar heists. But for years, security officials had warned that the regime’s cyberattacks were becoming increasingly sophisticated, looting enormous sums to support North Korea’s military and nuclear-weapons program.