Thanks to a law from the 1930s establishing a similar relationship between Swiss banks and their clients as lawyer-client confidentiality, Swiss banks have long been known for their secrecy. That secrecy was threatened recently when a massive leak of data from the iconic Swiss bank, Credit Suisse (CS  ), revealed the unscrupulous people using the bank's services.

Of the 18,000 bank accounts exposed in the so-called "Suisse Secrets" leak dating back to the 1940s, around 100 were held by private U.S. citizens, but none were held by American public figures. Most damningly, the leak shows that the bank continued to work with customers even after their accounts had been flagged as suspicious.

Among the accountholders outed in the documents were several officials tied to terrorist activity and human rights abuses, including the sons of a Pakistani intelligence chief, General Akhtar Abdur Rahman Khan. Khan helped to fund the mujahedeen in the 1980s with billions of dollars in aid funneled from countries like the U.S.

In 1985, then-president Ronald Reagan called for more oversight on Afghanistan's aid. Soon after, Khan's sons' accounts were opened, and the General was never officially charged with stealing the aid money. According to the records, the account in Khans' sons' names grew to hold $3.7 million.

There were also 25 accounts linked to corruption in Venezuela holding roughly $270 million total. Accounts were also opened by officials and children of officials working with the U.S. on the war on terror. The New York Times reports that other account holders include the mega-wealthy and businessmen facing sanctions.

The Times also reports that the illegal behavior by many of the leaked accountholders would have been easily discovered through a simple online search by bank officials.

While Swiss banks are protected by confidentiality laws, they are also required not to take money from entities tied to criminal activity. However, according to Daniel Thelesklaf, the former head of Switzerland's anti-money laundering agency, the law against this behavior is rarely enforced.

Credit Suisse spokesperson Candice Sun is arguing that the recent leak is part of "a concerted effort to discredit the bank and the Swiss financial marketplace, which has undergone significant changes over the last several years."

"Credit Suisse strongly rejects the allegations and inferences about the bank's purported business practices," sun told reporters. Sun said that many of the leaked accounts were created in "a time where laws, practices and expectations of financial institutions were very different from where they are now."

"Of the remaining active accounts, we are comfortable that appropriate due diligence, reviews and other control related steps were taken, including pending account closures," Sun continued.

This leak is only the most recent in a series of bank data leaks, including the 2016 Panama Papers, the 2017 Paradise Papers, and 2021's Pandora Papers. Each of these revelations has shed more light on the ways banks allow the ultra-wealthy and wealthy criminals to move massive amounts of money without facing any taxes or regulations.

Credit Suisse has been accused of nefarious behavior in the past, as well. In 2014, the bank pleaded guilty to allegations that it had worked to help Americans file fake tax returns. It paid $2.6 billion in fines and penalties as a result. Just three years later, the bak paid another $5.3 billion to settle allegations surrounding its mortgage-backed securities. Last year, it paid another $475 million to settle bribery allegations.

Former Suisse employees told prosecutors that the bank continues to secretly operate accounts for U.S. citizens, despite its 2014 guilty plea.