Cyber-thieves have made at least $25m (£19m) from ransomware in the last two years, suggests research by Google.
The search giant created thousands of virtual victims of ransomware to expose the payment ecosystem surrounding the malware type.
Most of the money was made in 2016 as gangs realised how lucrative it was, revealed a talk at Black Hat.
Two types of ransomware made most of the money, it said, but other variants are starting to emerge.