Capital One said the hack affected 100 million individuals in the United States

A tech engineer in the western US state of Washington was arrested Monday on charges of stealing sensitive data from more than 100 million credit card applications at financial heavyweight Capital One.

Paige Thompson, 33, a former Seattle technology company software engineer, was nabbed by FBI agents after she boasted about the data theft -- one of the biggest to hit a financial services company -- on the information sharing site GitHub, authorities said.

"The intrusion occurred through a misconfigured web application firewall that enabled access to the data," a statement by the US attorney's office in Washington said.

"On July 17, 2019, a GitHub user who saw the post alerted Capital One to the possibility it had suffered a data theft."

It said the Virginia-based bank that specializes in credit cards contacted the FBI after confirming the data theft, which took place between March 12 and July 17 of this year.

"According to Capital One, the data includes data regarding large numbers of (credit card) applications, likely tens of millions of applications," according to the criminal complaint.

In a statement, Capital One said the hack affected 100 million individuals in the United States and six million in Canada.

"Importantly, no credit card account numbers or log-in credentials were compromised and over 99 percent of social security numbers were not compromised," the bank said.

"Sincerely apologize"

Thompson, who used the alias "erratic" in online conversations, allegedly posted several times about the theft on GitHub and on social media.

One posting on a Twitter account with the user name "erratic" read: "I've basically strapped myself with a bomb vest, f**king dropping capital ones dox and admitting it," according to the complaint.

Authorities said electronic storage devices containing a copy of the stolen data were recovered at her residence on Monday.

Capital One said some of the information in the applications stolen, such as social security numbers, is encrypted or tokenized. Other information including names, addresses, dates of birth and credit card history was not secured.

The company said it expects the breach to cost between $100 to $150 million in 2019. It added that free credit monitoring and identity protection would be made available to anyone affected.

"While I am grateful that the perpetrator has been caught, I am deeply sorry for what has happened," Richard Fairbank, the company's chairman and CEO, said in a statement. "I sincerely apologize for the understandable worry this incident must be causing those affected and I am committed to making it right."

Thompson faces up to five years in prison and a $250,000 fine if convicted of on the charge of computer fraud.

She was ordered held in jail Monday pending a detention hearing later this week.

News of the Capital One breach comes after US credit monitoring agency Equifax last week agreed to pay up to $700 million to settle a similar incident that hit the company in 2017, affecting nearly 150 million customers.

The penalty was the biggest ever in a data breach case and followed revelations that hackers had stolen the personal details of millions, including names, dates of birth and social security numbers.