A bug is affecting a large number of systems running Windows and the security software from CrowdStrike. Airlines, train companies, health and emergency services are among those facing an issue causing repeated restarts and the blue screen of death (BSOD).

Microsoft says of the issue: “We have been made aware of an issue impacting Virtual Machines running Windows, running the CrowdStrike Falcon agent, which may encounter a bug check (BSOD) and get stuck in a restarting state. We are aware of this issue and are currently investigating potential options Azure customers can take for mitigation.”

The issue appears to be caused by CrowdStrike's Falcon Sensor agent, a part of its security platform. An apparent advisory from the security company has been posted across Reddit and X that appears to acknowledge the issue and recommend a potential fix. Crowdstrike has not publicly published the advice, however.

The Falcon Sensor is commonly used to protect Windows machines and that's evident by the number of companies, organisations and services reporting outages today.

UK news broadcaster Sky News was offline for the morning. It has since managed to restart its service. Though some companies will take longer to get up-and-running again, such as KLM, the major airline out of the Netherlands, which has had to suspend operations. Other airlines have reported disruptions, including Ryanair.

Various football clubs, airports, and banks have reported outages. London Gatwick has confirmed it is impacted by the outage but still recommends passengers arrive at a regular time for their flights. Berlin and Schiphol airport are both affected, though many are reporting they are operating as normal. 

A user on X suggests an airport in India has resorted to using hand-written boarding passes rather than the usual printed ones. 

There are reports of other airports facing major IT shutdowns and delays or cancellations. GP services in England are also said to be affected.

Citing the Australian National Cyber Security Coordinator Michelle McGuiness, Reuters reports there's currently no evidence to suggest it's a cyber attack.

The issue may take some time to resolve fully. Systems in constant boot loops are a nightmare to troubleshoot, update, or rollback to previous updates, as many PC builders can surely attest to. No doubt we should think of the poor IT workers—they're in for a long day. 

Microsoft engineers may be in for an especially rough patch, as a separate Microsoft 365 issue is leaving some users high and dry for access to 365 apps and services. This, however, is said to be caused by Microsoft's own messing around, not an external service.