If you experienced a flight cancellation, a postponed medical procedure, or encountered the blue screen of death on your PC, you’re likely aware of the widespread tech outage that hit globally early Friday.

A malfunctioning software security update led to a major breakdown in computer systems worldwide, impacting commercial flights, hospital operations, financial services, and media broadcasts.

The problematic update came from CrowdStrike, a top cybersecurity firm used by over half of Fortune 500 companies. This update contained a flaw that affected Microsoft’s Windows Operating System. Users of Mac and Linux systems were not impacted.

CrowdStrike clarified that this outage was “not a security incident or cyberattack,” and engineers are currently working with clients to resolve the issues.

So, where did these internet disruptions occur?