Scores of New Zealand online retail sites have been hacked and are infected by credit card skimming software that can steal customers' payment information, a security researcher has found.
The stores run vulnerable, unpatched versions of the Magento shopping cart software.
Unknown criminals are using security holes in the vulnerable systems and inject malicious code written in Javascript, according to Willem de Groot, who runs a Magento hosting company in the Netherlands.
As unsuspecting customers go to pay for their goods and services, the malware silently copies their credit card details and sends them to a server believed to be in Russia, hosted on a provider known to harbour cyber criminals.
The Javascript malware first appeared in November 2015, but de Groot said the number of hacked sites has jumped by more than two-thirds since then and now stands at over 5,900 worldwide.