The ransomware locks down all the files on an infected computer and asks the computer’s administrator to pay in order to regain control of them. “Affected machines have six hours to pay up and every few hours the ransom goes up,” said Kurt Baumgartner, the principal security researcher at security firm Kaspersky Lab. “Most folks that have paid up appear to have paid the initial $300 in the first few hours.”
The ransomware, called “WannaCry,” is spread by taking advantage of a Windows vulnerability that Microsoft released a security patch for in March. But computers and networks that haven’t updated their systems are at risk. The exploit was leaked last month as part of a trove of NSA spy tools.