Citigroup said today that computer hackers may have gained access to data on hundreds of thousands of card customers in North America.

An estimated one percent of customer accounts had been compromised but no actual numbers were given by the company.

City Cards, which is one of the biggest credit card providers with over 21 million accounts, has according to its 2010 annual report generated over $77bn in receivables last year.

In a statement the company said: “During routine monitoring, we recently discovered unauthorised access to Citi’s account online.”

The customers’ data affected by the breach included account numbers, names, contact information and emails.
Debit cards and customer information including dates of birth, social security numbers and card security codes have not been compromised the bank said.