The United States’ federal authorities on Monday announced the arrests of 74 people on three continents for their alleged roles in large-scale Business Email Compromise (BEC) schemes, according to announcements by the US Department of Justice and the Federal Bureau of Investigation (FBI).

Forty-two people were detained in the US, 29 in Nigeria, and three in Canada, Mauritius, and Poland following a coordinated international effort called Operation WireWire. The operation was conducted over six months before leading to a wave of arrests over a span of more than two weeks.

In a typical BEC scenario, a criminal uses various techniques, including computer intrusions and social engineering, to dupe a company employee into carrying out a transfer of funds. The victim labors under the impression that the funds are being sent to a trusted business partner, but instead the money ends up in a bank account controlled by the scammers.

The individuals charged in the WireWire operation are believed to have participated in international criminal organizations that defrauded small- to large-sized businesses, as well as individual victims, who were duped into transferring high-dollar amounts or sensitive records.

A number of those arrested are “money mules” who, whether acting as witting or unwitting accomplices, were recruited to receive funds from the victims and to wire them as directed by the fraudsters. These money launderers get to keep a small cut of the proceeds in exchange for their “trouble”.

“This operation demonstrates the FBI’s commitment to disrupt and dismantle criminal enterprises that target American citizens and their businesses,” FBI Director Christopher A. Wray was quoted as saying. “We will continue to work together with our law enforcement partners around the world to end these fraud schemes and protect the hard-earned assets of our citizens. The public we serve deserves nothing less.”

The US Department of Homeland Security, Department of the Treasury and the Postal Inspection Service, as well as law enforcement in Nigeria, Poland, Canada, Mauritius, Indonesia, and Malaysia, also contributed to the operation.

The FBI recently announced that the reported loss totals for victims of BEC fraud and its variation known as Email Account Compromise (EAC) fraud topped $676 million last year.