Arrests and searches have taken place in Yorkshire and the Humber as parted a nationwide operation to target suspected cyber criminals.
The focus was on people suspected of using cyber tools to get around anti-virus computer protection.
Today police revealed that four arrests were made at addresses in the Wales, Yorkshire and Humber, South Eastern and Eastern regions between June 5 and June 9.
Another 31 'cease and desist' visits were made to young people described as first time offenders or people on the fringes of offending who may not realise the dangers posed by malware.
Senior investigating officer David Cox, from the NCA’s National Cyber Crime Unit, said: "Regional Organised Crime Units across the UK have taken swift effective action against those who attempt to use malicious software, and have also played a vital part in deterring young offenders from committing cyber crimes in the future."
At the heart of the investigation is a platform used by malware developers before they launch cyber attacks.
It allows them to test samples for their ability to evade popular off the shelf anti-virus software.
Data shared with international partners by Europol’s European Cybercrime Centre (EC3) and the Joint Cybercrime Action Taskforce (J-CAT) triggered investigations across Europe.
In the UK, the NCA used the data to identify individuals who had uploaded and tested malware, and passed their details to cyber crime specialists in the Regional Organised Crime Units.
Mr Cox said: "I think a lot of people who put anti-virus protection on their computers would be astonished that there is a whole industry dedicated to trying to get around that protection. It’s why keeping antivirus software up to date is so important.
"Malware that has been tested through Counter Anti-Virus platforms poses a significant criminal threat to the UK, as demonstrated by the recent WannaCry attack.
"Law enforcement is working collaboratively and proactively to prevent and mitigate further attacks. Denying criminals the ability to test their malware before deploying it can severely disrupt their success and their profit margins."
Last month's WannaCry attack used malicious software to hold workers hostage by freezing their computers.
It wreaked havoc on some 47 NHS organisations before spreading to more than 100 countries across the world.
Detective Chief Inspector Vanessa Smith, of West Yorkshire's Cyber Crime Unit and the Regional Cyber Crime Unit, said: "The Yorkshire and the Humber Regional Cyber Crime Team have been working with the NCA and the four local forces and partners to conduct a series of cease and desist visits, which have led to valuable community intelligence being obtained. Individuals have been referred into partnerships to deter and prevent offending.
"We would urge all users to ensure that when downloading anti virus or any other software they obtain it from a reputable supplier to minimise the risk of the software being compromised.
"We would still advocate people using up-to-date antivirus software and updating relevant software this will in itself minimise the risk of being a victim of cyber crime."