Credit card readers in "dozens" of stores around the world were infected with the "Chewbacca" Trojan horse, designed to steal shoppers' information, a computer security firm announced.
According to the American RSA Security, the malware was detected in 12 countries, including the US, Russia and Canada - the rest are not named.
The stolen credit card numbers were transmitted to a central server set up by unknown hackers, which has now been taken down. The affected stores were notified by RSA.
The malicious code was disguised as a print handler file. It was named "Chewbacca" after the welcome page displayed by the hackers' server, which featured the familiar Star Wars character.
The stolen data was routed through the "dark" Tor network, which is used to hide a user's identity when surfing the Internet.
The Chewbacca case is not the first of its kind. As the BBC points out, in late 2013, infected cash registers at the American chain Tiger stole the details of 40 million credit and debit cards, while a similar attack was detected at luxury goods stores Neiman Marcus.
In the wake of the cyberattacks, the FBI issued a warning to retailers about the risk of tampering with checkout equipment.
