Banking giant HSBC has said that 15,000 Private Bank customers may have been affected by a data breach that occured approximately three years ago.
A former HSBC employee called Herve Falciani is under investigation in connection with the theft of the data, an HSBC spokesperson told ZDNet UK on Friday. The bank is not sure how the data was stolen, but said that it may have been transferred using a portable computer.
Falciani is alleged to have stolen the data during a project to transfer the information to a more secure system, said HSBC. He was caught at the beginning of 2008 trying to sell the data to different Lebanese banks, said the spokesperson.
In a statement, HSBC said that clients of HSB Private Bank Suisse and HSBC Guyerzeller who held accounts which were opened before October 2006, may have been affected.
"We deeply regret this situation and unreservedly apologise to our clients for this threat to their privacy," said Alexandre Zeller, chief executive of HSBC Private Bank Suisse, in the statement. "We are determined to protect our clients' interests and are taking every necessary measure to do so, actively contacting all our clients with Swiss-based accounts."
The Associated Press said in a report on Thursday that the data, which was confidential in Switzerland, could lead to HSBC international clients being open to prosecution from tax authorities in their countries.
A criminal investigation is being conducted by Swiss and French police. The French authorities have informed the Swiss authorities that the data they hold "will not be used inappropriately" said HSBC, who did not rule out the possibility that HSBC customers could be prosecuted by tax authorities in their own countries.
The criminal investigation against Falciani, which is being led by the Swiss Federal Prosecutor, is ongoing.