According to authorities, last November the men - from Russia, Estonia and Moldova - hacked into RBS WorldPay's systems and compromised the encryption used by the processor to protect customer data on payroll debit cards.

They then allegedly raised the limits on accounts before handing over 44 counterfeit payroll debit cards to a network of "cashers" who withdrew over $9 million in less than 12 hours from more than 2100 ATMs in at least 280 cities worldwide, including in the US, Russia, Ukraine, Estonia, Italy, Hong Kong, Japan and Canada.

The indictment alleges that the "cashers" were allowed to keep 30% to 50% of the stolen funds, but transmitted the bulk of the money back to defendants.

Once the money was stolen, the hackers tried to destroy data stored on the card processing network to hide their work, say authorities. However, RBS WorldPay spotted the unauthorised activity and reported the breach.

Sergei Tsurikov, 25, from Tallinn, Estonia, Viktor Pleshchuk, 28, of St Petersburg, Russia, Oleg Covelin, 28, from Chisinau, Moldova and a person known only as "Hacker 3" face a 16-count indictment charging them with conspiracy to commit wire fraud, wire fraud, conspiracy to commit computer fraud, computer fraud, access device fraud and aggravated identity theft.

Igor Grudijev, 31, Ronald Tsoi, 31, Evelin Tsoi, 20, and Mihhail Jevgenov, 33, all from Tallinn, have been indicted for access device fraud.

Tsurikov, Ronald Tsoi, Evelin Tsoi and Jevgenov were arrested earlier this year in Estonia. Tsurikov is awaiting extradition to the US.

Acting US Attorney, Sally Quillian Yates, Northern District of Georgia, says: "Last November, in just one day, an American credit card processor was hacked in perhaps the most sophisticated and organized computer fraud attack ever conducted. Today, almost exactly one year later, the leaders of this attack have been charged. This investigation has broken the back of one of the most sophisticated computer hacking rings in the world."