The hackers, who are not named in the indictment, then raised the withdrawal limits on prepaid MasterCard debit accounts issued by the National Bank of Ras Al-Khaimah, also known as RakBank, which is in United Arab Emirates.

Once the withdrawal limits have been eliminated, “even a few compromised bank account numbers can result in tremendous financial loss to the victim financial institution,” the indictment states. And by using prepaid cards, the thieves were able to take money without draining the bank accounts of individuals, which might have set off alarms more quickly.

With five account numbers in hand, the hackers distributed the information to individuals in 20 countries who then encoded the information on magnetic-stripe cards. On Dec. 21, the cashing crews made 4,500 A.T.M. transactions worldwide, stealing $5 million, according to the indictment.

While the street crews were taking money out of bank machines, the computer experts were watching the financial transactions from afar, ensuring that they would not be shortchanged on their cut, according to court documents.