Westpac is offering its personal and business online banking customers a free 12-month subscription to BitDefender Internet Security 2012.
The bank had previously offered a free subscription to PC Tools' security software under a deal struck in 2007.
The BitDefender suite performs anti-virus, anti-spyware, social networking security and firewall functions, and is available to Westpac, St.George, Bank SA and Bank of Melbourne customers via online banking portals.
A Westpac spokeswoman said the bank had decided to switch from PC Tools to BitDefender following an "internal evaluation process".
She noted that the BitDefender suite included support for Apple's Mac OS, now used by seven percent of Westpac's online banking customers.
Most major banks offer security software as a free or discounted service to help combat rising levels of online fraud.
Suncorp and ANZ Bank offer customers discounted PC security software by AVG and Norton, while NAB is "reviewing a security software offering" after discontinuing its offer of discounted ZoneAlarm and PC Tools software.
Meanwhile, Commonwealth Bank's online banking customers have access to free, six-month subscriptions to McAfee Internet Security for both PC and Mac users.
A Commonwealth Bank spokesman said Mac OS logins to its online banking service, NetBank, had grown in recent years to account for about 10 percent of all desktop logins currently.
Financial institutions have considered banning jailbroken mobile devices and requiring customers to install anti-virus software as a prerequisite for using online banking services, but no official action has yet been taken.
Fraud is estimated to cost Australians approximately $8.5 billion a year, according to the Australian Institute of Criminology. The divide between businesses and consumers on the figure remains unclear.