Westpac struck by fourth major outage this week

Westpac is dealing with yet another outage, leaving customers without access to their money for the fourth day in a row.

Millions of customers have been affected by the outages, which also blocked customers from its mobile app and online services for hours on Monday, Tuesday and Wednesday.

WATCH THE VIDEO ABOVE: Westpac customers outraged.

One customer previously told 7NEWS they could not access their cash and could not even pay for petrol because their cards were not working.

Reports of the outage on Down Detector show a dip overnight, with reports picking up again on Thursday morning.

However, customers online say they have not had access to their accounts for multiple days.

Westpac has not revealed what is behind the ongoing disruptions.

Monash University cybersecurity professor Nigel Phair described the outages as “extremely rare” and “extremely unusual” for modern banking systems.

7NEWS understands the ongoing issues have been referred to the government’s lead cybersecurity agency, with the major concern that the big four bank has been compromised.

“When something like that happens it enlivens the cybersecurity part of our government,” Treasurer Jim Chalmers said.

Experts say the disruptions have the hallmarks of a “denial of service” (DoS) attack, preventing users from accessing services they would usually be able to.

Westpac has refused to rule out a cyberattack or hack but did say there has been no risk to customer data or accounts, which fits the “denial of service” theory.

“Money and data are safe enough, it’s the inconvenience that goes with it all,” Phair said.

‘Sorry for the disruption’

Westpac on Wednesday thanked customers for “your patience” and said again it was “sorry for the disruption”.

“In recent days Westpac customers may have experienced issues logging into their mobile or online banking,” the bank said in a statement shared on X, formerly Twitter.

“We’re sorry for the disruption. We know how important it is to have access to online banking.”

Westpac said its teams are “working around the clock” and claimed services were restored, though customers hit back at this.

“No advice from Westpac,” one customer said online.

“What is going on? When will this be fixed? I have bills to pay urgently.

“Total lack of communication from Westpac.”

“Please be transparent,” another customer said.

“What’s exactly going on and how long should we wait? The system is still down.”

The bank has not provided any updates since Wednesday.

In its last statement to customers, it said it would “continue to actively monitor the situation”.

“You do not need to take any action. Customers are encouraged to be vigilant of potential scams at this time as some scammers may use a service disruption as an opportunity to impersonate the bank, offering help.”