Upon reports that J.P. Morgan and at least four other banks have been victims of a cyber attack, the firm says it's working with law enforcement to determine its scope. A coordinated attack on major banks this month led to the theft of customer data that could be used to take money out of accounts, according to Bloomberg, which cited an individual briefed by U.S. law enforcement. It reports that the FBI is investigating whether Russian hackers attacked the firms in retaliation for sanctions on the country over the Ukraine conflict. J.P. Morgan says as the bank learns more, it will contact anyone it determines may have been impacted by the attack.

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