Four men were arrested by the Dutch National High Tech Crime Unit and charged with stealing an estimated $1.4 million by using the banking malware known as TorRat.
Dutch-speaking users were targeted by the remote-access trojan, which is designed to steal online banking credentials.
Using Tor, the infamous anonymous network, for their command-and-control servers, the alleged perpetrators were able to hide their commands and the communication flow between compromised computers and the servers controlled by the gang. Funds were stolen from at least 150 Dutch bank accounts.
Authorities have not revealed how they uncovered the operation, but according to reports, the investigation may be linked to the recent arrest of 28-year-old Irishman Eric Marques. In September, the FBI confirmed that it exploited a Firefox vulnerability that aided in its investigation against Marques.