Hackers breached Citibank's systems early last month and may have made off with the personal data of hundreds of thousands of customers, the bank has revealed. The data breach—which Citi admitted after being questioned by the Financial Times—exposed customers' names, account numbers, and contact information. But information like Social Security numbers and card security codes was not compromised, according to the bank.
Citi believes the hack attack, which was discovered during routine monitoring, affected some 1% of its 21 million customers. The bank says only credit card customers were affected, but the Times has spoken to several customers who say their debit cards were compromised. Analysts say it's very unusual for a financial institution to be attacked directly, as hackers tend to avoid their secure servers in favor of stealing account information indirectly. "For the actual breach to happen at a bank is a very big deal," says an analyst at Gartner Research. (Read more Citibank stories.)