HSBC confirmed yesterday that 10 of its wealthiest customers have had data about them stolen, but it was claimed today that as many of 4,000 clients have been affected.HSBC learned of the security breach at its private banking arm in Geneva after a prosecutor interviewed the person suspected of stealing the information.But, while the bank says only 10 clients are affected, France's Le Figaro newspaper claims that up to 4,000 French clients were named on the list. The stolen list is understood to include 3,000 French clients with Swiss bank accounts who are suspected of tax evasion.