Is there a major bank that didn't manipulate the London interbank offered rate (Libor)? First to be hit was Barclays in June 2012 with a $450 million settlement, and then UBS AG was forced to pay $1.5 billion in December 2012.

This time, the European Commission has multiple targets. The Commission announced on Dec. 4 that six different companies would be charged a total of 1.7 billion euros ($2.3 billion) for rigging interest rates associated with Libor, the single-highest cartel penalty leveled by the Commission. Deutsche Bank AG received the largest single penalty at 725 million euros ($985 million), while Royal Bank of Scotland Group Plc received a fine of 391 million euros ($531 million).

In a statement, Joaquín Almunia, the Commission vice president in charge of competition policy, said that he was surprised not that the manipulation occurred, but rather the cooperation between banks to make it work.

“What is shocking about the LIBOR and EURIBOR (Euro Interbank Offered Rate) scandals is not only the manipulation of benchmarks, which is being tackled by financial regulators worldwide, but also the collusion between banks who are supposed to be competing with each other,” Almunia said.

Almunia added that “healthy competition and transparency” are necessary to a fully functioning economy, and he hopes the large fines will send a message that this type of collusion will be treated harshly moving forward.

The charges stem from allegations that the banks manipulated Libor for mutually shared greater profits, often using chat rooms and other outside sources to work together in manipulation. One trader told Bloomberg that he regularly asked “four or five banks in general” to set high or low fixings for a given rate. Another said that he had “a vested interest in making sure our fixings match.”

Other than Barclays and UBS, additional firms have also been implicated in the Libor scandal, even in the United States. Brokerage firm ICAP must pay $90 million for its part in the scandal, while a criminal investigation into several firm employees is still pending.

And the Commission may not be done yet. Four companies withdrew from settlement negotiations — JPMorgan Chase, HSBC Holdings and Credit Agricole withdrew from the Euribor settlement while ICAP withdrew from further Libor settlements. According to the Commission, all four continue to face an antitrust probe.

For more on the ongoing Libor manipulation stories, check out these InsideCounsel stories: