Hackers have conducted the largest bank heist ever

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.