On Friday afternoon, a little-known computer program triggered an IT meltdown that took down digital infrastructure on a global scale.

Seemingly all at once, millions of computers around the world became unusable and unable to be rebooted, showing what's known in the industry as the "Blue Screen of Death".

The ABC's broadcast systems were some of the earliest to be visibly affected, with computer after computer inexplicably breaking down, leaving journalists scrambling to deal with the exact issue they were trying to report on.

"It's possible we'll have difficulties updating this story due to computer systems affecting us here at the ABC," wrote the ABC's Joseph Dunstan on the blog at 4pm AEST.

Meanwhile, the ABC's TV presenters continued to broadcast without teleprompters or on-screen graphics.

The scale of the outage — which some experts have called unprecedented — soon became clear as reports came in from almost every conceivable business.

Airports were thrown into chaos. Check-outs at supermarkets were down. Government departments, emergency services, universities, law firms, mines, media — no industry seemed to be spared.

Lucas and Liz Gibson were caught at Sunshine Coast airport, unable to check in for their scheduled flight to Sydney.

"The service desk staff can't help, computers are down, they don't know what's going on, they're just waiting and seeing," Mr Gibson told the ABC.

It was mid-afternoon in Australia when it first hit, while other parts of the globe were still sleeping.

From Berlin to Dubai, the United States to India, the problem was the same.

"Across Europe, at airports in Spain, in Germany, there have been incidents that have been reported at almost all of the airports," said the ABC's Michelle Rimmer in London.

As the massive scope of the outage was still revealing itself, its cause was already being dissected online.

There was early speculation that Microsoft was responsible, largely because only computers running the US tech giant's operating systems had been affected.

Adding to the confusion was that Microsoft had reported a major technical outage with its cloud services earlier in the day.

Ultimately though, that was a red herring.

Microsoft would later attribute the issue to "an update from a third-party software platform". 

A little-known culprit

Less than an hour after computers had begun melting down, another US-based software company began to be linked to the outage.

CrowdStrike — valued at $125 billion at the close of US markets overnight — was being named by multiple affected organisations.

"Like a number of other organisations, global issues affecting CrowdStrike and Microsoft are disrupting some of our systems," said a Telstra spokesperson.