Part of the 6.7 billion yen ($60 million) worth of cryptocurrencies hacked from Cryptocurrency Exchange Zaif apparently went through a “mixing service” that made tracking those Bitcoins virtually impossible, according to an Asahi Shimbun investigation.
The process involved dispersing the Bitcoins to several thousand accounts after transferring them into what is presumed to be the hacker’s account.
Osaka-based Tech Bureau Corp. announced Sept. 20 that the Zaif exchange it operates was hacked last week and virtual currencies valued at about 6.7 billion yen were illicitly transferred.
According to Tech Bureau officials, the hacking occurred between 5 p.m. and 7 p.m. on Sept. 14, resulting in three cryptocurrencies being taken–Bitcoin, Monacoin and Bitcoin Cash.
The Asahi Shimbun learned that 5,966 Bitcoins were transmitted to a certain outside account from 1,726 accounts that appeared to belong to Tech Bureau after examining the online cryptocurrency transactions. The value of the virtual currency transactions matched the value of the stolen Bitcoins in the recent alleged cryptocurrencies theft.
Officials of Tech Bureau admitted the link between the discovered transaction records and the illicit withdrawals of cryptocurrencies from its Zaif exchange.
The withdrawn Bitcoins were then dispersed to several thousand accounts.
The hacker apparently exploited a mixing service that made the transactions of the cryptocurrencies virtually anonymous and difficult to track.
The recent massive theft was the second such attack on the Japanese cryptocurrency exchange this year. Hackers made off with the equivalent of 58 billion yen in digital currency called NEM, operated by Tokyo-based Coincheck Inc., in January.
Of the cryptocurrencies snatched from the Zaif exchange, about 4.5 billion yen represented assets deposited with the company by customers while 2.2 billion yen represented Tech Bureau assets.
The Financial Services Agency (FSA) conducted an on-site inspection of Tech Bureau on Sept. 20 after the company reported the theft to the FSA and Osaka prefectural police.
The FSA has twice ordered Tech Bureau to improve operations by dealing with shortcomings in its internal management structure.
The agency will investigate to ascertain how the cryptocurrency theft occurred and decide on punishment for Tech Bureau.