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FBI assessing how much damage done in JPMorgan cyberattack

Cyber thieves broke into America's biggest bank, JPMorgan Chase and federal agents are investigating.

Sources say the cyberattack happened earlier this month and now the FBI and Secret Service are trying to determine how much damage has been done.

A cyber thief may have gained unauthorized access to the data at JPMorgan Chase by hacking into the personal computer of a single bank employee. Some private account information was reportedly compromised. But so far, JPMorgan Chase has not seen any unusual fraud activity.

In a statement the bank said: "Companies of our size unfortunately experience cyberattacks nearly every day. We have multiple layers of defense to counteract any threats and constantly monitor fraud levels."

Law enforcement and industry sources say this breach appears to be the work of criminal hackers, possibly working in Russia.