According to HSBC Private Bank, the Swiss authorities earlier this month passed data files to the bank which showed that client information had been compromised.

As a result, the bank is contacting customers to explain and apologize for the threat to their privacy, said HSBC, adding that the bank doesn't believe that the stolen data has or will allow any third party to access any client account.

The data theft, said HSBC, was done by a former IT employee about three years ago, involves existing clients who had accounts with the bank in Switzerland before October 2006.