The parent firm of Citi Private Bank has suffered a massive computer hacking attack, resulting in hundreds of thousands of bank card holders having their details compromised, this publication can report.

The Financial Times has reported that Citigroup said about 1 per cent of its card customers were affected by the breach, unearthed back in May during routine monitoring by the US banking giant. Information such as account numbers and contact information was compromised.

Citi was quoted by media as saying that the breach had not however compromised data such as birth dates, social security numbers, card expiration dates and card security codes.

There is no knowledge of the firm's private banking clients being affected, but this could not be confirmed at present.

The report adds to a number of cases of large firms, such as EMC, Lockheed Martin and Sony suffering cyber attacks.

The issue of client security has become a key concern at banks, including the wealth management side of such businesses. In Switzerland and Liechtenstein, for example, some private banks, such as HSBC in Geneva and LGT in Liechtenstein, have suffered the theft of client data.