2014 JPMorgan Chase data breach

The 2014 JPMorgan Chase data breach was a cyberattack against American bank JPMorgan Chase that is believed to have compromised data associated with over 83 million accounts—76 million households (approximately two out of three households in the country) and 7 million small businesses. The data breach is considered one of the most serious intrusions into an American corporation's information system and one of the largest data breaches in history.

Source: Wikipedia — 2014 JPMorgan Chase data breach (CC BY-SA 4.0)