In 2008, an employee of HSBC stole the details of 24,000 Swiss bank accounts from his employer. Now that data is being used across Europe to investigate tax evasion.

HSBC revealed earlier this year that IT worker Hervé Falciani stole the data from its Swiss subsidiary over the course of many months.

Falciani, who has said he wanted to raise awareness of the insecurity of the bank’s IT systems, handed the data over to French authorities, although it has been alleged that he tried to sell the data in the Lebanon first.

In March 2010, Falciani claimed that he had been kidnapped by the Israeli intelligence agency Mossad, which he says was investigating links between HSBC and Lebanese political and paramilitary group Hezbollah.

Whatever the truth of the matter, the data has been used in tax evasion investigations in France, Italy and now Spain. According to Finextra, Spanish officials have gained access to the details of around 3,000 Swiss bank accounts containing as much as €6 billion.