An external security investigator notified Capital One on 17 July and the breach was confirmed on 19 July. The FBI has arrested the alleged hacker and taken them into custody.
The Financial Times reports that the suspect is Paige Thompson, a former Amazon Web Services employee. She was arrested earlier this week and appeared in court in Seattle.
In a statement, Capital One confirmed that the breach affected around 100 million individuals in the US and approximately six million in Canada. The company says that no credit card numbers, log-in credentials or social security numbers, were compromised.