Investigators are calling it the biggest blow against cyber criminals: in an operation in several countries, more than 100 servers worldwide were seized and 1,300 domains were taken out of service.

This was announced by the Frankfurt am Main Public Prosecutor’s Office, the Federal Criminal Police Office (BKA) and Europol on Thursday morning. Several of the currently most influential malware families have been taken offline. The operation was primarily aimed at the groups behind the six malware families “IcedID”, “SystemBC”, “Bumblebee”, “Smokeloader”, “Pikabot” and “Trickbot”. This is special software that can be used to gain access to other people’s computers for criminal purposes.

According to the information, ten international arrest warrants were issued and four people were provisionally arrested in the measures coordinated by German authorities. Germany issued arrest warrants against a total of eight actors. On this basis, seven people are being sought who are strongly suspected of “having participated as members of a criminal organization for the purpose of distributing the Trickbot malware,” the investigators further announced.

During the operation on Tuesday and Wednesday, searches were carried out in a total of 16 properties in Armenia, the Netherlands, Portugal and Ukraine, during which numerous pieces of evidence were seized. The data seized are currently being evaluated and could lead to further investigations.

“With the largest international cyber police operation to date, the law enforcement authorities have managed to deal a significant blow to the cybercrime scene,” said BKA Vice President Martina Link, according to the statement. “The current success is based on measures against infrastructures, actors and their financial resources.”

Law enforcement officials from the Netherlands, France, Denmark, Great Britain, Austria and the USA were involved in the operation. They were supported by the police authority Europol and the European Union Agency for Criminal Justice Cooperation.