Attackers have stolen almost $500,000 worth of the Ethereum Classic digital currency by carrying out a compute-intensive hack that rewrote its blockchain, officials with Coinbase, one of the leading crypto currency exchanges, said on Monday.
The heist was the result of carrying out what's known as a rollback attack, which allowed the attackers to reorganize the Ethereum blockchain, Coinbase security engineer Mark Nesbitt said in a blog post. From there, the attackers were able to "double spend" about 88,500 ETC, meaning they were able to recover previously spent coins and transfer them to a new entity. As a result, the coins were effectively transferred from the rightful recipients to new entities chosen by the attackers.
"We observed repeated deep reorganizations of the Ethereum Classic blockchain, most of which contained double spends," Nesbitt wrote. "The total value of the double spends that we have observed thus far is 88,500 ETC (~$460,000)."