JPMorgan Says Data Breach Hit 76 Million Households

IMAGE DISTRIBUTED FOR JP MORGAN CHASE - Jamie Dimon, JP Morgan & Chase Co. Chairman and CEO, discusses the impact of The
IMAGE DISTRIBUTED FOR JP MORGAN CHASE - Jamie Dimon, JP Morgan & Chase Co. Chairman and CEO, discusses the impact of The Fellowship Initiative, Monday, June 23, 2014, at JPMorgan Chase Headquarters in New York. The expanded Fellowship Initiative enrolls young men of color in Chicago, Los Angeles, and New York City in a multi-year hands-on enrichment program that includes academic, social and emotional support. (Photo by Diane Bondareff/Invision for JPMorgan Chase/AP Images)

A cyber attack at America's biggest bank this summer affected more than half of all U.S. households -- far, far more than previously estimated, and the latest in a string of massive, unnerving data breaches.

The attack at JPMorgan Chase affected the data of 76 million households and 7 million businesses, the bank said in a regulatory filing on Thursday.

That impact was far bigger than earlier estimates that about 1 million customers had been affected, the New York Times noted. It represents more than half of the roughly 115 million households in America.

Hackers attacked the bank's computer systems periodically between mid-June and mid-August, according to The Wall Street Journal. The attackers accessed customer names, email addresses, phone numbers and physical addresses, along with "internal JPMorgan Chase information relating to such users," the bank said in its regulatory filing. The bank didn't describe what sort of information that was.

The bank said it has seen no evidence that "account numbers, passwords, user IDs, dates of birth or Social Security numbers" were taken, and it has not yet seen any signs of fraudulent activity using the leaked data.

JPMorgan Chase representatives did not immediately return a request for further comment on the breach, which is under investigation by the FBI. Earlier on Thursday, a NYT report on the JPMorgan filing mistakenly suggested that the bank had suffered a second major breach. The paper has since corrected that story.

For context on the size of this breach, a recent cyber attack against Home Depot affected 56 million customer cards, in what was reported to be the biggest retail hack in history. Late last year, a data breach at Target affected roughly 40 million customers at the height of the holiday shopping season.