A data leak from Credit Suisse, Switzerland's second-largest bank, revealed details of more than 30,000 accounts – some of them unpleasant – according to a German newspaper and other media on Sunday, pointing to apparent failures of due diligence in checks on many customers.

Credit Suisse said in a statement that it “strongly rejects the allegations and insinuations about the bank’s purported business practices.”

Sueddeutsche Zeitung, a German newspaper, said it acquired the data anonymously over a year ago through a secure digital mailbox. It stated that it was unclear whether the source was an individual or a group, and that no money or promises were made by the newspaper.

The newspaper said it analyzed the data alongside the Organized Crime and Corruption Reporting Project and dozens of media partners, including The New York Times and The Guardian, from the 1940s until well into the last decade.

According to the report, the bank has accepted customers who are "corrupt autocrats, suspected war criminals, and human traffickers, drug dealers, and other criminals."

Credit Suisse stated that the claims are "mostly historical" and "are based on fragmentary, erroneous, or selective material taken out of context, leading in tendentious interpretations of the bank's business activity."

What did the Suisse Secrets probe reveal?

A human trafficker convicted in the Philippines, a Hong Kong stock exchange chairman imprisoned for bribery, and an Egyptian billionaire who ordered the assassination of his Lebanese pop star girlfriend are among those exposed.

According to the media sites, other clientele includes multiple leaders of state and government, ministers, intelligence officials, as well as oligarchs and businesses with shady backgrounds.

A former Siemens manager was listed as having six accounts after being convicted of bribery in 2008.

One of the former Siemens executives' accounts had assets worth more than 54 million Swiss francs (about €51.66 million) in 2006, according to the publication, which cannot be attributed to his Siemens income.

The revelation also discloses the hidden accounts of Jordan's King Abdullah II, Iraq's former Deputy Prime Minister Ayad Allawi, Algerian ex-President Abdelaziz Bouteflika, and Armenia's ex-President Armen Sarkissian's.

Money laundering

Earlier, Credit Suisse was accused in a Swiss court of allowing a suspected Bulgarian cocaine trafficking ring to launder millions of euros, some of which were hidden in suitcases.

Swiss prosecutors are seeking around 42.4 million Swiss francs ($45.86 million) in compensation from Credit Suisse in the first criminal trial of a major bank in Switzerland (CSGN.S).

They claim that between 2004 and 2008, the country's second-largest bank and one of its former relationship managers failed to take all necessary steps to prevent alleged drug traffickers from hiding and laundering cash.

Was anyone probed? 

The leak reveals Credit Suisse's pervasive inability to conduct due diligence in analyzing and rejecting questionable clients and those managing illegal funds.

OCCRP wrote on its website that reporters spoke with several former bank employees who described a "highly toxic corporate culture that incentivized taking on risk to maximize profits — and bonuses."

Former employees claimed that this resulted in a culture where there were two sets of rules for two types of clients: the wealthy and the ultra-wealthy.

Swiss banking secrecy is "immoral", according to the whistleblower, whose identity is undisclosed to the media partners.

"The pretense of protecting financial privacy is just a fig leaf to cover up the shameful role of Swiss banks as collaborators with tax evaders," the whistleblower said.