In total, the eight people indicted face charges ranging from wire fraud, computer fraud and access device fraud to aggravated identity theft and conspiracy.  The hacking ring is based in Eastern Europe, with prosecutors indicating they are in Russia, Moldova and Estonia.

Specifically, the hacker ring raised red flags after compromising the RBS Worldpay computer network, which is the Royal Bank of Scotland Group processing division, when they cloned prepaid ATM card information.  Once they had the necessary information, they were able to withdraw money from more than 2,100 ATM machines.

According to a Wired article, Oleg Covelin, 28, from Chisinau, Moldova; Sergei Tsurikov, 25, from Tallinn, Estonia; Viktor Pleschchuk, 28, of St. Petersburg, Russia; and a fourth person, "Hacker 3," are accused of "perhaps the most sophisticated and organized computer fraud attack ever conducted."

The data breach took place last November, according to RBS Worldplay, with the company publicly announcing the network issue in December.  A total of 1.5 million cardholders were affected by the breach, which security experts say could happen again to other organized hacker groups.

Although this hacker group has been busted by the feds, there are still many other unknown hacker groups based in the same region, security analysts note.