Visa Secure is a security protocol that helps to prevent fraud on online credit and debit card transactions. It is used to authenticate a customer when a payment is being processed. Authentication will be completed using a one-time password that is sent to your mobile phone number held with Bank Australia. You should ensure that your mobile phone number (and all contact details) are correct so that you do not encounter any difficulties.
Look for the Visa Secure symbol as a sign the merchants value your business and your security.