A gang that made more than $72m (£45m) peddling fake security software has been shut down in a series of raids.
Co-ordinated by the FBI, the raids were carried out in the US, UK and six other countries.
The money was made by selling software that claimed to find security risks on PCs and then asked for cash to fix the non-existent problems.
The raids seized 40 computers used to do fake scans and host webpages that tricked people into using the software.
About one million people are thought to have installed the fake security software, also known as scareware, and handed over up to $129 for their copy. Anyone who did not pay but had downloaded the code was bombarded with pop-ups warning them about the supposed security issues.
Raids conducted in Latvia as part of the attack on the gang allowed police to gain control of five bank accounts used to funnel cash to the group's ringleaders.
Although no arrests are believed to have been made during the raids, the FBI said the computers seized would be analysed and its investigation would continue.
The raids on the gang were part of an international effort dubbed Operation Trident Tribunal. In total, raids in 12 nations were carried out to thwart two separate gangs peddling scareware.
The second gang used booby-trapped adverts to trick victims. Raids by Latvian police on this gang led to the arrest of Peteris Sahurovs and Marina Maslobojeva who are alleged to be its operators.
According to the FBI, the pair worked their scam by pretending to be an advertising agency that wanted to put ads on the website of the Minneapolis Star Tribune newspaper.
Once the ads started running, the pair are alleged to have changed them to install fake security software on victims' machines that mimicked infection by a virus. On payment of a fee the so-called infection was cured. Those that did not pay found their machine was unusable until they handed over cash.
This ruse is believed to have generated a return of about $2m.
"Scareware is just another tactic that cyber criminals are using to take money from citizens and businesses around the world," said assistant director Gordon Snow of the FBI's Cyber Division in a statement.