By Savannah Meacham and Samantha Lock in Sydney

Knock-on effects from the unprecedented global IT outage have eased at Australian businesses but the cost to the economy remains unknown.

Banks, media outlets, airports, supermarkets, retailers, government services and hospitals were left scrambling as a result of the outage on Friday afternoon.

Authorities say it was caused by major cyber security firm CrowdStrike deploying a software update with a defect, not a malicious cyber attack.

Home Affairs and Cyber Security Minister Clare O’Neil said on Saturday the outage was likely the largest in history but the focus had turned to making sure all businesses were back up and running.

“This has been a very serious incident for the Australian economy,” she said following a National Co-ordination Mechanism meeting with CrowdStrike representatives.

Ms O’Neil said there would be significant questions about how CrowdStrike handled the outage and the cost to the country and consumers.

With most companies operational, despite small teething issues such as delays at airports and some supermarket check-outs being closed, a new concern has emerged.

Ms O’Neil warned scammers were taking advantage of the outage to target Australian consumers and businesses with phishing emails, texts and calls.

Emails pretending to be from Microsoft or CrowdStrike are being sent asking Australians to send bank or personal details to access a software reboot.

The nation’s cyber-intelligence organisation, the Australian Signals Directorate, has also warned people to beware of hackers releasing malicious websites and code purporting to help fix the outage.

Ms O’Neil urged Australians to stay vigilant of suspicious activity and to report it to ScamWatch.

“Don’t give any personal information and certainly don’t put in any bank details or money,” she said.

Businesses were left to clean up the mess created by the outage with airports bearing the brunt of the hindrances.

Melbourne travellers suffered the most delays on Saturday morning with the rescheduling of Jetstar’s 150 cancelled flights from the previous night.

Some flights were still cancelled, including more than a dozen Jetstar and some Qantas, Virgin, Rex and United Airlines flights, the airport said.

But all airports around the nation, including Melbourne, have returned to normal operations.

“We will continue to work closely with our airlines and airport community to monitor and support recovery over the coming days,” Melbourne Airport general manager of operations Scott Dullard said.

Supermarkets were back online on Saturday after some shoppers were forced to abandon trolleys full of goods during the outage.

Woolworths and Coles said all stores were open and operational on Saturday but warned some check-outs were still unavailable.

The majority of Dan Murphy’s and BWS stores have opened as usual but some have altered opening hours.

Online and delivery services are still impacted with orders made on Friday likely to take some time to be completed, a spokesperson said.

Ms O’Neil asked Australians to be patient as services come back to normal.

“Don’t take this out on the staff at your supermarkets if you have to wait a little bit longer, it is absolutely not their fault,” she said.

The IT outage prompted federal politician Bob Katter to demand cash remains in circulation amid the “danger” of relying on digital technology.

“This a wake-up call that the risk associated with a cashless society is too high for us to pay,” Mr Katter said.

A significant concern raised by the outage was the vulnerability of global IT systems.

Cyber Security Cooperative Research Centre CEO Rachael Falk told ABC Breakfast it should be a wake-up call for businesses and governments because the impacts would have been catastrophic if it had been a cyber attack.

Prime Minister Anthony Albanese is on leave but will be briefed regularly on the outage.