US House leaders are calling on CrowdStrike CEO George Kurtz to testify to Congress about the cybersecurity company’s role in sparking the global tech outage that grounded flights, knocked banks and hospital systems offline and cut services.

CrowdStrike said this week a “significant number” of the millions of computers that crashed last Friday, causing global disruptions, were back in operation as its customers and regulators awaited a more detailed explanation of what went wrong.

Republicans who lead the US House Homeland Security committee said on Monday (local time) they wanted those answers soon.

“While we appreciate CrowdStrike’s response and coordination with stakeholders, we cannot ignore the magnitude of this incident, which some have claimed is the largest IT outage in history,” Mark E. Green of Tennessee and Andrew Garbarino of New York wrote in a letter to Kurtz.

They added that Americans “deserve to know in detail how this incident happened and the mitigation steps CrowdStrike is taking”.

A defective software update sent by CrowdStrike to its customers disrupted airlines, banks, hospitals and other critical services Friday, affecting about 8.5 million machines running Microsoft’s Windows operating system. The painstaking work of fixing it has often required a company’s IT crew to manually delete files on affected machines.

CrowdStrike said in a blog post on Sunday that it was starting to implement a technique to accelerate remediation of the problem. It also said in a brief statement on Monday that it was actively in contact with congressional committees.

Shares in the Texas-based cybersecurity company have fallen more than 20 per cent since the meltdown, knocking off billions of dollars in market value.

The scope of the disruptions has also caught the attention of US government regulators, including antitrust enforcers, though it remains to be seen if they take action against the company.

Scam warning for Australians

Home Affairs Minister Clare O’Neil has warned it could take weeks for the outage issues to fully resolve.

“There has been a huge amount of work over this weekend to get the economy back up and running. However, it will take time until all affected sectors are completely back online,” she said on Sunday.

“In some cases we may see teething issues for one or two weeks.

“There is no impact to critical infrastructure or government services.”

O’Neil has also warned Australians to “be really careful” about scammers looking to exploit the outage.

“If someone has called you and is suggesting that they’re going to help you, talk you through a reboot of your system, I would hang up the phone,” she said on Saturday.

“Be really careful and be really on the lookout for attempts to use this to scam Australians, and to scam small businesses.”

Australian Chamber of Commerce chief executive Andrew McKellar has also warned that companies affected by Friday’s outage are unlikely to receive compensation.

“For many businesses, it’s going to be very difficult to secure direct compensation, but obviously, that’s something that should be looked at,” he said.

“If there are ways to consider how that might be evaluated, then obviously that’s something that should be on the table.

“It is a reminder, regrettably, for a lot of businesses this is going to be water under the bridge, it’s going to be a learning experience.”

-with AAP