The FBI, with the assistance of the NSA, is investigating a suspected hacking attack against JP Morgan Chase that resulted in the leak of gigabytes of sensitive data.

According to "two [unnamed] people familiar with the probe", the Feds are working on the theory that Russian hackers hit US banks in retaliation for US sanctions imposed as a result of the ongoing conflict in the Ukraine.

Ordinary cyber-criminals are not suspected because of the sophistication of the attack. Rather, state-backed hackers are suspected. Amichai Shulman, CTO at data center security firm Imperva, said that indications that the attacks resulted in no initial financial loss point towards a politically motivated attack.

“Companies of our size unfortunately experience cyber attacks nearly every day,” Patricia Wexler, a JPMorgan spokeswoman, told Bloomberg in an email. “We have multiple layers of defense to counteract any threats and constantly monitor fraud levels.”

Shulman explained: "None of the people commenting on the incident mentioned a direct financial loss, or a direct fraudulent financial activity by the attacker. Everyone is talking about grabbing sensitive information. I find it odd that someone who was actually able to break into a bank is not using it for making immediate profit.

"Two possibilities here: the first is that there are missing pieces in the puzzle (ie, we are not being told everything) and second is that these were indeed politically motivated hackers."