South Korean regulators are investigating cryptocurrency exchange Bithumb after a technical error briefly credited users with nearly $40 billion worth of Bitcoin that did not actually exist — a phenomenon now being described as “ghost Bitcoin.” The incident occurred on February 6, when Bithumb was running a promotional campaign meant to credit users with 2,000 won (about $1.37) each. Instead, due to an internal input error, an employee mistakenly entered the payout unit as Bitcoin rather than won. As a result, 620,000 “ghost Bitcoin” — valued at roughly $40 billion — suddenly appeared across hundreds of customer accounts on the exchange, said a Bloomberg report.