Citigroup confirmed a security breach at Citi Account Online, which was discovered by the authorities recently during a routine monitoring. The names, account numbers and contact information, including email addresses of the customers have been compromised. More critical information like date of birth, social security numbers, card expiration date and card security code (CVV) have not been accessed by the hackers, Citi said.

The US bank said that they are in the process of applying more secure measures for online banking system and are contacting the customers whose data have been compromised. Citi also confirmed that around 1 per cent of their card customer base has been affected.

Citi reported to have notified law-enforcement authorities about the incident. With the latest development Citi joins the long list of corporations that have been wading through tough waters, due to hacker attacks. Recently Sony, PBS, Nintendo, Fox and an affiliate agency of FBI have been threatened by hackers, LulzSec. The people behind Citigroup are unknown and the company is yet to reveal any details about the hackers.

The Financial Times first reported the Citigroup data breach.