How to fix a Windows PC affected by the global outage

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The update was intended for CrowdStrike’s Falcon software, which is “endpoint detection and response” software designed to protect companies’ computer systems from cyberattacks and malware. But instead of working as expected, the update caused computers running Windows software to crash and fail to reboot. Home PCs running Windows are less likely to have been affected, because CrowdStrike is predominantly used by large organizations. Microsoft did not immediately respond to a request for comment.

“The CrowdStrike software works at the low-level operating system layer. Issues at this level make the OS not bootable,” says Lukasz Olejnik, an independent cybersecurity researcher and consultant, and author of Philosophy of Cybersecurity.

Not all computers running Windows were affected in the same way, he says, pointing out that if a machine’s systems had been turned off at the time CrowdStrike pushed out the update (which has since been withdrawn), it wouldn’t have received it.

For the machines running systems that received the mangled update and were rebooted, an automated update from CloudStrike’s server management infrastructure should suffice, he says.

“But in thousands or millions of cases, this may require manual human intervention,” he adds. “That means a really bad weekend ahead for plenty of IT staff.”