The FBI has cracked a pair of international scareware rings that stole as much as $74 million.
US authorities said 960,000 people had been affected by the first scam, which installed fake antivirus on people's computers.
The criminals used malicious websites to infect users, who were then hit with a barrage of pop-ups badgering them to buy the fake antivirus for as much as $129. The criminals pulled in $72 million.
The second scam used online advertising to infect users, stealing $2 million.
The criminals allegedly submitted a normal, malware-free advertisment to run on a Minneapolis newspaper's website. Once the ad had gone live, the criminals changed the code, infecting users of the site with malware that froze machines.
"Users' computers 'unfroze' if the users paid the defendants for the fake antivirus software," the FBI said. "Users that failed to purchase the fake antivirus software found that all information, data and files stored on the computers became inaccessible."
The FBI arrested two Latvians, Peteris Sahurovs, 22, and Marina Maslobeojeva, 23 for the latter scam. They face up to 30 years in prison. No arrests appear to have been made in the first case.
As part of its raids, the FBI also picked up 22 computers in the US, as well as 25 across Europe - including the UK - and said the Metropolitan Police was one of several international police forces that supported the investigation.
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