New York - The FBI said it's working with the Secret Service to determine the scope of recently reported cyber attacks against several US financial institutions.
A report on Bloomberg.com said on Wednesday that the FBI is investigating an incident in which Russian hackers attacked the US financial system this month in possible retaliation against US government-sponsored sanctions aimed at Russia.
The attack, Bloomberg said, led to the loss of sensitive data. Bloomberg cited security experts saying that the attack appeared "far beyond the capability of ordinary criminal hackers".
The New York Times, citing people familiar with the matter, said JPMorgan Chase and at least four other firms were hit this month by co-ordinated attacks that siphoned off huge amounts of data, including cheque and savings account information.
JPMorgan spokesperson Trish Wexler said large companies experience cyber attacks nearly every day.
"We have multiple layers of defence to counteract any threats and constantly monitor fraud levels," said Wexler, who did not confirm the reports.
The Wall Street Journal cited unnamed sources in a report that called the attacks a "significant breach of corporate computer security".
JPMorgan is the largest US bank by assets.
The FBI said in a statement that combating cyber threats and criminals remains a top priority for the US government and that it's "constantly working with American companies to fight cyber attacks".