FBI Said to Examine Whether Russia Tied to JPMorgan Hacking

Russian hackers attacked the U.S. financial system in mid-August, infiltrating and stealing data from JPMorgan Chase & Co. and at least one other bank, an incident the FBI is investigating as a possible retaliation for government-sponsored sanctions, according to two people familiar with the probe.

The attack resulted in the loss of gigabytes of sensitive data, said the people, who asked not to be identified because the probe is still preliminary. Authorities are investigating whether recent infiltrations of major European banks using a similar vulnerability are also linked to the attack, one of the people said.