TOKYO -- The cryptopirates who late last month made off with about $530 million worth of the digital currency NEM from a Japanese exchange have converted about $84.7 million of the booty into other virtual coins.
The trades are being made on the dark web, which can only be accessed with anonymity-providing tools.
The NEM coins were stolen from Coincheck, which had been a popular exchange for Japanese cryptocurrency investors. Coincheck remains closed but has started to refund any yen that its clients held at the exchange. It has yet to say when it might begin giving clients access to their cryptocurrency holdings.
The hackers are converting their NEM into other digital assets to head off investigators and to circumvent NEM Foundation monitors.
It is becoming increasingly difficult to track the stolen NEM.
The NEM Foundation is marking the accounts into which stolen coins are being moved. But as the number of accounts receiving these coins increases, the foundation is falling behind. It now takes the foundation two or three minutes to mark an account, by which time the coins could have already moved into another account.
Some digital security experts believe the heist was pulled off by an individual or a small group, given what they say is the haphazard nature of the crime. They point out that the dark site set up to facilitate trades for other cryptocurrencies was not even established until a week after the hack. The experts inclined to this theory say a pro would have prepared the site beforehand.
The hack began in the early hours of Jan. 26. The cryptocurrency was then moved into nine accounts, and then to about 400 accounts through the beginning of this month.
Sometime around Feb. 7, a dark site advertised it would sell NEM at a 15% discount for other cryptocurrencies.
Three days later, The Nikkei reported that $4.6 million of the stolen NEM had been converted into other cryptocurrencies.
On Saturday, Takayuki Sugiura, president of L Plus, a Tokyo-based information security company, said about 9 billion yen ($84.7 million) of the stolen NEM is believed to have been converted into bitcoin and other cryptocurrencies.
The yen value is based on the NEM rate at the time of the heist.
More recently, the hacker or group of hackers might have found another way to convert the loot. Since the beginning of the month, the party responsible is believed to have sent NEM on numerous occasions to an account at an exchange based in New Zealand, presumably to take advantage of lax background checks.