Credit Suisse Group AG and Barclays Plc have recently agreed to settle the charges against them lodged by the U.S. Securities and Exchange Commission and New York's Attorney General.

The allegation is that the two banks have misled investors in the way their trading platforms were managed.

Credit Suisse is required to pay $84.3 million, $24 million of which will go to the SEC for interest and disgorgement, and the remainder to be shared between the two institutions. According to the US SEC, Barclays is ordered to pay $70 million, the biggest fine imposed on an operator of dark pool.

The authorities have investigated the two banks if they have disclosed sufficient information to their clients regarding their dark pool trading. It appears that the authorities have seen Barclays misrepresenting the way it monitored its dark pools for high frequency trading.

According to New York Attorney General Eric Schneiderman, Credit Suisse methodically routed its clients' orders to the bank's own dark pool, but told them that it didn't favor any special trading venue.

Dark pools started in the 1980s. They are private stock markets operating inside some of the biggest banks in Wall Street. This system of trading enables market traders to buy and sell big blocks of stock without informing other traders. Trading in dark pools over the years has risen to 20 percent of the total amount that is exchanged in the stock market every day.

"These cases mark the first major victory in the fight against fraud in dark pool trading that began when we first sued Barclays: coordinated and aggressive government action, admissions of wrongdoing, and meaningful reforms to protect investors from predatory, high-frequency traders," said Schneiderman.

"We will continue to take the fight to those who aim to rig the system and those who look the other way," he added.