An indictment unsealed Thursday accused Lajud-Pena and the other seven New York suspects of withdrawing $2.8 million in cash from hacked accounts in less than a day.
Arrests began in March.
Lajud-Pena was found dead with a suitcase full of about $100,000 in cash, and the investigation into his death is continuing separately. Dominican officials said they arrested a man in the killing who said it was a botched robbery, and two other suspects were on the lam.
The first federal study of ATM fraud was 30 years ago, when the use of computers in the financial community was growing rapidly. At the time, the Bureau of Justice Statistics found nationwide ATM bank loss from fraud ranged from $70 and $100 million a year.
By 2008, that had risen to about $1 billion a year, said Ken Pickering, who works in security intelligence at CORE Security, a white-hat hacking firm that offers security to businesses.
He said he expects news of the latest ring to inspire other criminals.
"Once you see a large attack like this, that they made off with $45 million, that's going to wake up the cybercrime community," he said.
"Ripping off cash, you don't get that back," he said. "There are suitcases full of cash floating around now, and that's just gone."
Associated Press technology writer Peter Svensson in New York, national writer Martha Mendoza in San Jose, Calif., and writer Ezequiel Abiú López in Santo Domingo, Dominican Republic, contributed to this report.
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