United States bank Capital One said a hacker gained access to more than 100 million credit card applications earlier this month.
The compromised data included some Social Security numbers.
The Department of Justice said Monday that Paige Thompson, 33, was arrested in connection with the breach.
The department alleges that Thompson “posted on the information sharing site GitHub about her theft of information from the servers storing Capital One data.”
Thompson was able to gain access by exploiting a misconfigured web application firewall, the DOJ said.
Capital One indicated it fixed the vulnerability and said it is “unlikely that the information was used for fraud or disseminated by this individual.” However, the company is still investigating.
The breach affected around 100 million people in the United States and about 6 million people in Canada, according to Capital One.
However, “no credit card account numbers or log-in credentials were compromised and over 99% of Social Security numbers were not compromised,” the company said.
Capital One is headquartered in McLean, Virginia. It is ranked 10th on the list of largest banks in the United States by assets.