The suspects were accused of working for the Russian Main Intelligence Directorate, a military agency in the Russian army, according to the U.S. Department of Justice.
Researchers at Talos Intelligence Group have noticed a sharp rise in DNS requests connected with its command-and-control servers since the end of August.
The digital currency exchange said one of its private key holders was cooperating with authorities on an investigation and had been out of touch.
The New York financial regulator has criticized the lack of leadership at Twitter which made it easier for the hackers to infiltrate the platform.
The Ethereum Classic blockchain has implemented a defense mechanism, "MESS," to reduce the chance of a 51% attack taking place on the network
The exchange has also taken steps to recover some of the stolen coins in partnership with some of the digital currency projects.
The attack was carried out by a sophisticated team of hackers that may have been state-sponsored, according to local media reports.
As much as $1 billion worth of Ethereum tokens are at risk from attack because they are missing a software standard released back in 2017.
The digital currency tax reporting service suffered a breach, resulting in 13,000 rows of data and 1,082 customer email addresses stolen.
The team of hackers is reportedly controlled by Bureau 121, the division with responsibility for cyber warfare in the rogue state.
Security breaches might be due to an exchange’s embrace of open-source libraries that reduce the time and effort needed to launch their platforms.