Australian banks are among about 100 from around the world that have fallen victim to an unprecedented hacking attack, an international cyber-security company says.

Security company Kaspersky Lab said more than $1.2 billion had been stolen by hackers from a number of banks and financial institutions in the past two years across 30 countries, including Australia.

The firm said it had been investigating with Interpol to track down the criminals.

Authorities believe a group of multi-national hackers from Russia, China, Ukraine and parts of Europe use a type of virus known as Carbanak malware to access bank employee computers and ultimately get inside their networks.

Once they gain access, they can mimic the actions of cash transfer staff after watching how they operate.

The hackers then transfer money from the bank into off-shore accounts, or order the bank's ATMs to dispense cash to a waiting criminal.

The thefts mostly targeted central accounts as opposed to customer accounts and usually took up to $10 million in each raid.

Of the big four Australian banks, ANZ said it was not affected, while the Commonwealth, Westpac and National Australia Bank declined to comment on this particular attack.

In a statement, a Commonwealth Bank spokesman said cyber security was of the utmost importance.

"We don't comment on cyber-security matters, however, we have systems and measures in place that actively monitor and protect our customers," it said.

Banks and financial institutions in the USA, Russia, Germany and China were among the others affected.

Kaspersky Lab Australia said the company would not release details about which institutions were hit in Australia for commercial confidentiality reasons.

Kaspersky Lab spokesman Sergey Golovanov said the attacks were very sleek and professional.

"The attackers didn't even need to get into the bank's services; once they got into the network, they learned how to hide the money transaction activities behind particular actions," he said.

The Australian Federal Police said it had not received a referral relating to the matter from the banking sector.