Hackers broke into the computer networks of at least five US banks and siphoned off gigabytes of data, which included chequing and savings account information of millions of customers, the New York Times reports. Security experts are describing the attack as "extremely sophisticated".
The intrusions were first reported by Bloomberg, which said that the attacks were the work of Russian hackers and theorized that the motivation might have been the low point in relations between Russia and the West. But security experts and government officials told the Times they had not yet made that conclusion.
According to Bloomberg:
In one case, the hackers used a software flaw known as a zero-day vulnerability in one of the banks' websites. They then plowed through layers of elaborate security to steal the data, a feat security experts said appeared far beyond the capability of ordinary criminal hackers.
It's not clear which other banks have been affected yet. JPMorgan has said that despite the attacks, it has not seen any increased fraud levels. [The New York Times]