A new strain of ransomware — malicious software that encrypts a computer’s files and then demands payment to unlock them — spread rapidly around the world on Friday. This map shows tens of thousands of Windows computers that were taken hostage by the software, a variant of the WannaCry ransomware, that were recorded by the security blog MalwareTech.

While the map does not show every computer that was infected by the ransomware, it shows that the attack struck simultaneously in many countries around the globe. MalwareTech collected the data by taking control of one of the domain names used in the attack.