The Commonwealth Bank of Australia (CBA) is now offering some 2.3 million customers access to free SMS authentication as the final phase in its two-factor authentication program for its Internet banking service, NetBank.

The CBA's group executive for retail banking services, Michael Cameron, said NetBank now provides access to NetCode SMS, a free service which allows customers with a mobile phone to receive a one-time code to authorize certain transactions.

Last month, 30,000 "highly active" NetBank customers were sent a token which also produces a NetCode unique to the token, which automatically changes every 30 seconds. The customer inputs the NetCode into NetBank during login.

"Customers tell us that stronger Internet security is important and so we have decided to make NetCode security available to all NetBank customers. All customers can now register for NetCode SMS within NetBank," Cameron said.

According to the CBA, NetBank is the only Australian online banking service to provide all customers with access to their choice of free two-factor authentication.

"Our trials of SMS security have confirmed that it is the best option for most customers. It is simple and convenient. We also have the option of a token, which some of our more active customers will prefer. Our approach is to match the security solution to the banking needs of the customer," Cameron said, adding the CBA will continue to develop NetBank's security features to ensure its customers are protected from fraudsters.

Customers can register for NetCode SMS in NetBank or find out more by visiting http://netbank.com.au/sms.