What is CrowdStrike, the cybersecurity company linked to the global Microsoft outage?

The widespread Microsoft outage that grounded flights, knocked hospitals and banks offline, and disrupted broadcasters and businesses across the world stemmed from an issue with cybersecurity company CrowdStrike, Microsoft said in a statement Friday.

CrowdStrike is a cybersecurity and cloud tech company based out of Austin, Texas, that launched around 2011. It has more than 10 different platforms and tools that focus on cyber threat protection and IT tools according to its website.

The security company’s clients include nearly 300 Fortune 500 companies, and its tools are used by companies including Target, Salesforce, and T-Mobile.

Here’s what you need to know.

The global outage impacting IT systems around the world disrupted a mix of public and private entities, including airlines, banks, railways, and hospitals early Friday morning.

According to CrowdStrike’s CEO, a technical issue affected IT systems using the cybersecurity technology on Microsoft Windows systems, particularly those running on Windows 10 software.

Microsoft said it was aware of the issue and that the underlying cause had been fixed, but that some Microsoft 365 apps and services would continue to be affected.

CrowdStrike’s CEO and cofounder, George Kurtz, says the issue was not because of a cyberattack, but rather a defect in a software update sent to Windows users, and that a fix has been deployed.

“CrowdStrike is actively working with customers impacted by a defect found in a single content update for Windows hosts,” Kurtz said. “Mac and Linux hosts are not impacted. This is not a security incident or cyberattack.”

Citing technical issues, American Airlines, United, and Delta all asked the Federal Aviation Administration for a global ground stop on all flights Friday morning. At least 540 flights in the U.S. were canceled, according to ABC.

Photos showed error messages impacting various computer screens across airport gates.

Flights that were already in air were allowed to continue on.

At least 103 flights into and out of the Philadelphia International Airport were delayed or canceled as of Friday morning, an airport spokesperson told The Inquirer.

Both Microsoft and CrowdStrike are publicly traded entities.

In turn, both companies saw impacts from the outage reflected in trades.

According to the Wall Street Journal, premarket trading showed Microsoft stock (MSFT) was down 2.9% at $427.70. Meanwhile, CrowdStrike shares (CRWD) were nearly 19% lower at $279.50.

The outage has impacted everything from universities to hospitals in some capacities because of the sheer number of public and private entities operating on Microsoft systems.

Thousands of trains were canceled in both the U.S. and Europe, some broadcast stations were silenced Friday morning, and hospitals reported technical difficulties (though it shouldn’t impact most patient services). Some hospitals, including Penn and Main Line Health in Philadelphia, canceled elective procedures, citing the difficulties.

Millions of Windows 10 users were met with ”blue screens of death” (also known as BSOD) following Microsoft’s major outage — the first sign many said they knew something was wrong.

“It looks like Windows didn’t load correctly. If you’d like to restart and try again, choose Restart my PC below,” the Windows error message said. But from there, users reported being unable to reboot, leaving them stuck.

As early as Thursday afternoon, millions of desktop PCs and laptops using CrowdStrike and operating on Windows 10 were hit with the damning blue screen — an issue related to a bug tied to an update to the Windows software, CrowdStrike has said.

On social media, photos showed airlines, classrooms, and others confronting the ominous page.

An update is being sent out to users impacted by the bug, Microsoft said.

CrowdStrike says users impacted should monitor the company’s customer support portal.