PALO ALTO, Calif. — 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.
The bank’s internal computers, used by employees who process daily transfers and conduct bookkeeping, had been penetrated by malware that allowed cybercriminals to record their every move. The malicious software lurked for months, sending back video feeds and images that told a criminal group — including Russians, Chinese and Europeans — how the bank conducted its daily routines, according to the investigators.
Then the group impersonated bank officers, not only turning on various cash machines, but also transferring millions of dollars from banks in Russia, Japan, Switzerland, the United States and the Netherlands into dummy accounts set up in other countries.
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.
The Moscow-based firm says that because of nondisclosure agreements with the banks that were hit, it cannot name them. Officials at the White House and the F.B.I. have been briefed on the findings, but say that it will take time to confirm them and assess the losses.