In late 2013, an A.T.M. in Kiev started dispensing cash at seemingly random times of day. No one had put in a card or touched a button. Cameras showed that the piles of money had been swept up by customers who appeared lucky to be there at the right moment.
But when a Russian cybersecurity firm, Kaspersky Lab, was called to Ukraine to investigate, it discovered that the errant machine was the least of the bank’s problems.
In a report to be published on Monday, and provided in advance to The New York Times, Kaspersky Lab says that the scope of this attack on more than 100 banks and other financial institutions in 30 nations could make it one of the largest bank thefts ever — and one conducted without the usual signs of robbery.