LONDON, July 19 (Reuters) - A global tech failure

disrupted operations across multiple industries on Friday,

halting flights and forcing a number of broadcasters off-air, as

the outage upended everything from banking to healthcare

systems.

WHAT HAPPENED?

CrowdStrike, a U.S. cybersecurity company, is among the most

popular in the world, counting more than 20,000 subscription

customers around the world.

According to an alert sent by CrowdStrike to its clients and

reviewed by Reuters, its widely-used "Falcon Sensor" software is

causing Microsoft Windows to crash and display a blue screen,

known informally as the "Blue Screen of Death".

The alert, which was sent at 0530 GMT on Friday, also shared

a manual workaround to resolve the issue.

WHY DID IT HAPPEN?

"The damage to business processes at the global level is

dramatic. The glitch is due to a software update of

CrowdStrike's EDR product," said Omer Grossman, Chief

Information Officer at identity security firm CyberArk.

EDR, or Endpoint Detection and Response, is a cybersecurity

product that companies place on their clients' computers to help

defend them from hackers. That software, which runs in the

background on clients' machines, or endpoints, is used by

cybersecurity firms to monitor for signs of attack on their

clients' networks.

"It turns out that because the endpoints have crashed - the

Blue Screen of Death - they cannot be updated remotely and the

problem must be solved manually, endpoint by endpoint. This is

expected to be a process that will take days," he added.

WHO HAS BEEN IMPACTED?

The global tech outage has affected operations in different

sectors internationally including at Spanish airports, U.S.

airlines and Australian media and banks.

The governments of Australia, New Zealand, and a number of

U.S. states are facing issues, while American Airlines ( AAL ),

Delta Airlines, United Airlines (UAL.O), and Allegiant

Air (ALGT.O grounded flights citing communication problems.

In Britain, Sky News, one of the country's major television

news channels, was off air on Friday.

WHY ARE SO MANY IMPACTED?

With the move to the cloud and with companies owning huge

market shares, their software is running on millions of

computers around the world.

"The damage to business processes at the global level is

dramatic," said Grossman.