How a software update from cyber firm CrowdStrike caused one of the world’s biggest IT blackouts

A fault with an update issued by cybersecurity company CrowdStrike led to a cascade effect among global IT systems Friday, with industries ranging from banking to airlines facing outages.

Banks and health-care providers saw their services disrupted and TV broadcasters went offline as businesses worldwide grappled with the ongoing outage. Air travel has been hit hard, too, with planes grounded and services delayed.

At the heart of the issue is Texas-based cybersecurity vendor CrowdStrike. On Friday, the cybersecurity firm experienced a major disruption following an issue with a software update.

So what happened, exactly? CNBC takes a look.

CrowdStrike is a cybersecurity vendor that develops software to help companies detect and block hacks. It is used by many of the world's Fortune 500 companies, including major global banks, health-care and energy companies.

CrowdStrike is what's known as an "endpoint security" firm as it uses cloud technology to apply cyber protections to devices that are connected to the internet.

This differs from alternative approaches used by other cyber firms, which involve applying protection directly to back-end server systems.

"Many companies use [CrowdStrike software] and install it on all of their machines across their organization," Nick France, chief technology officer at IT security firm Sectigo, told CNBC's "Squawk Box Europe" on Friday.

"So when an update happens that maybe has problems with it, it causes this problem where the machines reboot, and people can't get back into their computers."

On Friday, people around the world began encountering an error screen known as the "blue screen of death."

This issue — a common problem among PCs, for example if a machine overheats — was the result of an