Security researchers have discovered that a piece of malware named after the Star Wars character Chewbacca has been used to steal payment card and personal information 49,000 payment cards stored by 45 retailers in 11 countries.
Details from the payment cards were stolen from 24 million payment card transactions over two months, according to researchers from security company RSA.
The attack, which began on 25 October 2013, was mostly concentrated on US retailers, but the infection has also been detected in 10 other countries including Canada, Australia and Russia.
US retailer Target was recently the victim of a wide-scale security breach in its stores, when payment data relating to 40 million credit and debit cards, as well as 70 million customer records were stolen between 27 November and 15 December 2013.
In the Target case, cyber-criminals installed RAM scraper malware on Target's point-of-sale (POS) cash register systems that was capable of stealing information directly from the memory of the computer system.
RSA has not revealed how the malware gets installed on the computer systems linked to the retailers' cash registers, but it is typical that this malware is attached to phishing emails aimed at luring unsuspecting employees at these retailers into downloading and installing the software.
The ChewBacca malware contains a key-logger to record all keyboard inputs and windows that are opened on a victim's PC, as well as a memory scanner that scans all the information being processed in the memory of the cash register's computer system, looking for credit card payment details that are logged in the computer when the magnetic strip on the card is swiped (known as Track 1 and Track 2 data).
The malware then grabs the card number and logs it on the criminal's server.
ChewBacca was first spotted by Kaspersky Lab researchers in December, but what makes this version of the malware unique is that it has added Tor functionality.
The private Tor network enables anonymous on-line communications and is often used by cyber-criminals to hide their IP addresses. The new variant of the ChewBacca malware installs a Tor client onto the victim's computer system so that all traffic is hidden from the criminals' server to the cash register.
According to Kaspersky, this malware is not currently being marketed by its creator for sale on underground forums.
"The ChewBacca Trojan appears to be a simple piece of malware that, despite its lack of sophistication and defence mechanisms, succeeded in stealing payment card information from several dozen retailers around the world in a little more than two months," RSA said in the blog post.
"Retailers have a few choices against these attackers. They can increase staffing levels and develop leading-edge capabilities to detect and stop attackers (comprehensive monitoring and incident response), or they can encrypt or tokenise data at the point of capture and ensure that it is not in plaintext view on their networks, thereby shifting the risk and burden of protection to the card issuers and their payment processors."