JPMorgan is investigating a possible cyber attack on its systems and is working with the FBI to work out how severe it was.
Further reports say that up to seven of the top 15 US banks may have been targeted in a synchronised attack, although none of the other institutions involved have released statements as yet.
Although the bank said it had not seen any odd or possibly fraudulent activity, it has taken the precaution to secure its systems to prevent any sensitive or confidential information being exposed.
JPMorgan said it uncovered malicious software on its network, revealing it may have been the subject of a cyber attack, but did not reveal any further details.
JPMorgan spokeswoman Patricia Wexler did, however, brush off the severity of this most recent attack as a usual occurence.
She 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."
CNN reported that a person who analysed the attack said whoever was responsible had, "used sophisticated, never-before-seen malware to get deep enough into the banks' computer systems to delete and manipulate records."
However, Bloomberg said Russian hackers were thought to have been responsible for targeting JPMorgan and other US banks in mid-August and these attacks did result in the loss of sensitive data.
Earlier on Wednesday, the FBI said it was investigating possible cyber attacks on a number of financial institutions, but it did not disclose which organisations were involved.
FBI spokesman Joshua Campbell said: "We are working with the United States Secret Service to determine the scope of recently reported cyber attacks against several American financial institutions."
