Overnight, the Commonwealth Bank contacted thousands of customers after it identified unauthorised transactions made by one common merchant.
It cancelled and reissued as many as 8,000 cards as a result.
Some other banks have also been affected.
The incident highlights the need for consumers to be aware of the risks associated with credit card use, especially online, but also shows the effective responsiveness of banks' systems to identify such breaches.
For some tips on how to be more online savvy when using your credit card, I spoke with Ingrid Just from consumer advocate Choice, in this SBS World News Australia online only interview.
