Banks are lucrative targets for cybercriminals because of the large amounts of personal and financial customer data they hold, and big banks have previously been criticized for using outdated IT systems that dramatically increase the risks posed by cyberattacks.

But NAB’s strong performance before the standing committee on economics last Friday should allay fears that big banks are not doing enough to tackle cyber risks.

“We are active every day in identifying potential threats and stopping them, and we work closely with all authorities across the landscape to help with this,” NAB interim chief executive Philip Chronican told the commission last Friday.

"I didn't have any data until recently, but I know that every day there are attempts to attack our environment, and every day we fight back."

NAB CFO Gary Lennon revealed the bank's spending on cyber security has tripled to $150 million over the past five years. NAB has also created a cyber security summit for mid-sized business customers to ensure their expertise is passed on to their customer base.

ANZ also now employs over 200 people in its cyber security team, with spend in the hundreds of millions of dollars.

But CEO Shane Elliott notes that this has pushed attackers to other vulnerabilities.

"The weak point is the customers and/or other parts of the ecosystem, so they're much more likely to target, unfortunately, vulnerable people who are tricked into giving access to their accounts through passwords or other things," said Mr. Elliott vomited last Friday.

"We're seeing an increase in this kind of activity as a result of the fact that banking systems are actually incredibly secure," he said.

Mr Elliott also touched on the possibility of state-sponsored attacks, which are becoming more likely - and more devastating - as more countries engage in cyber warfare.

"We're constantly monitoring all parts of our network for risk and action, whether it's a low-level cyber risk, such as amateurs trying to break in, or whether it's sophisticated nation-state activity, etc.," said Mr. Eliot.

Westpac has also increased its spending and now invests more than $50 million a year to upgrade various cyber security facilities.

“Compared to a few years ago, I feel like we're in pretty good shape; but it's certainly nothing we can be happy about," Westpac chief executive Brian Hartzer told the standing committee on 8 November.

"I would also say that there is a lot more coordination and cooperation within the sector and between the sector and various government agencies to make sure that we share intelligence and continue to help each other to strengthen our defences."