The police found 600,000 e-mail addresses with passwords on Dutch servers of people who may have been affected by the rogue software (malware) Emotet.
People can check if their device might be infected through the police website.
Emotet is the name of a widespread type of malware that is often sent to victims as an attachment of emails via malicious links or infected Word documents.
Victims who inadvertently install Emotet on their computers open the door to other malicious software.
For example to steal data or to digitally take the device hostage.
After investigation, authorities mapped a network of hundreds of servers.
Two of the three main servers were in the Netherlands, the Public Prosecution Service (OM) reports Wednesday.
The police hacked it to disrupt the Emotet operation.
The OM speaks of an "important battle" in the fight against the criminal organization behind Emotet.
"You are dealing here with the absolute top in the field of cybercrime," explains public prosecutor Martijn Egberts.
The Dutch-based servers that the police have penetrated are now being used by the authorities to offer a software update that will quarantine Emotet.
"This is one of the first things where you can see where the hacking authority of the police (which has this authority since March 2019, ed.) Can lead to. It protects hundreds of thousands of victims and prevents - I dare say - hundreds of millions. to damage. "
OM: Several suspects in the picture
"The criminal organization behind Emotet has been active for years," says Egberts.
But finding out exactly who the suspects are is difficult, he says.
"It is quite easy to protect your identity as a cyber criminal," said the public prosecutor.
"These people are also quite capable of taking countermeasures to avoid detection. That makes it difficult to identify suspects."
Nevertheless, this has succeeded in a number of cases.
Egberts: "We have insight into several people. Who they are and what should be done with them (in terms of the strategy regarding arrests, ed.) Is part of international consultation."
"Have suspects been identified? Yes. Are there any Dutch people? No", says Egberts.
In addition, authorities suspect that more people are involved with Emotet than they are now known to.
The investigation is therefore still ongoing.