Digital heist that terrorised the world Robert Gren had 26 minutes left to decide whether to pay the ransom. It was Monday, May 15, three days after the global cyberattack now known as WannaCry had begun, and a clock on Gren’s computer screen was counting down.

Above the clock, there was a warning: “Payment will be raised on 5/15/2017 21:13:40.”

The ransomware on Gren’s desktop computer had encrypted his files and demanded he pay $300 in bitcoin to get them back. In 26 minutes, the price would double. He was willing to pay, because the files he’d lost represented his entire digital history: family photos, work files, music. It would all be gone. But he didn’t believe the hackers would decrypt his files even if he paid.

The ransomware that had just found its way onto Gren’s desktop was simultaneously installing itself onto tens of thousands of other Windows computers across Europe, Asia, and parts of North America. About 30 minutes after Gren’s screen had gone black, the National Health Service in the UK announced that computers in 16 of its health facilities had been infected. Doctors were unable to access patient records and emergency rooms were forced to turn people away. Soon, it was 33 facilities. Then there was a telecommunications company in Spain, a cell phone carrier in Russia, and the French automaker Renault. Anyone using certain versions of Windows that hadn’t been updated within the last month was vulnerable. Within hours, it was being called the most successful ransomware attack of all time.