NEW YORK — It was a huge bank heist — but a 21st-century version in which the robbers never wore ski masks, threatened a teller, or set foot in a vault.
Yet, in two precision operations that involved operatives in more than two dozen countries, the organization was able to steal $45 million from thousands of ATMs in a matter of hours.
In New York City alone, a team of eight people struck 2,904 machines on Feb. 19, withdrawing $2.4 million.
On Thursday, federal prosecutors in Brooklyn unsealed an indictment charging eight members of the New York crew — including their suspected ringleader who was found dead in the Dominican Republic on April 27 — offering a glimpse into what the authorities said was one of the most sophisticated and effective cybercrime attacks ever uncovered.
“In the place of guns and masks, this cybercrime organization used laptops and the Internet,’’ said Loretta E. Lynch, the US attorney in Brooklyn.
The indictment outlined how they were able to steal data from banks, relay that information to a far-flung network of ‘‘cashing crews,’’ and then launder the stolen money by buying high-end luxury items.
In the first robbery, hackers infiltrated the system of an unnamed Indian credit-card processing company that handles Visa and MasterCard prepaid debit cards.
The hackers — who are not named in the indictment — proceeded to raise the withdrawal limits on prepaid accounts issued by the National Bank of Ras Al-Khaimah, which is in United Arab Emirates.
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 ATM transactions worldwide, stealing $5 million, according to the indictment.
But that was just a prelude for what prosecutors said was a more brazen crime two months later. This time, the hackers infiltrated a US-based credit card processing company that also handles Visa and MasterCard prepaid debit cards. The company’s name was not revealed in the indictment.
After securing 12 account numbers for cards issued by the Bank of Muscat in Oman and raising the withdrawal limits, ‘‘cashing crews’’ were set in motion. Starting at 3 p.m. Feb. 19, the crews made 36,000 transactions and withdrew about $40 million from machines in various countries in about 10 hours.