December 11, 2012, 10:10 AM — Researchers from Israel-based IT security firm Seculert have uncovered a custom-made piece of malware that infected hundreds of point-of-sale (PoS) systems from businesses in 40 countries in the past few months and stole the data of tens of thousands of payment cards.
The malware was dubbed Dexter after a text string found in some of its components and infected Windows-based PoS systems belonging to big-name retailers, hotels, restaurants and even private parking providers, Seculert researchers said Tuesday in a blog post.
The company's researchers found a sample of the Dexter malware while investigating other threats, Aviv Raff, Seculert's chief technology officer, said Tuesday. After analyzing it, they were able to gain access to a command and control (C&C) server hosted in the Republic of Seychelles, where the malware uploaded the stolen payment card data, he said.
The Dexter malware sends a list of processes running on infected systems to the command and control server, Raff said. The attackers then check whether any of those processes correspond to specific PoS software and if they do, they instruct the malware to dump their memory and upload the data back to the server.
The memory dumps are then parsed with an online tool that runs on the server and can extract payment card "Track 1" and "Track 2" data from them. This is the information written on the magnetic stripes of payment cards and can be used to clone them, Raff said.
Since this is an ongoing attack it's hard to determine exactly how many PoS systems have been compromised so far, but it's probably between 200 and 300, Raff said. The total number of compromised payment cards is equally hard to estimate, but tens of thousands seems to have been compromised just in the past few weeks, he said.
According to statistics gathered from the C&C server, 30 percent of the infected PoS systems are located in the U.S., 19 percent in the U.K. and 9 percent in Canada. However, businesses from the Netherlands, Spain, South Africa, Italy, France, Russia, Poland, Brazil, Turkey and other countries have also been affected, painting the picture of a truly international criminal operation.
The origin of the attackers is unclear, but strings found in the malware suggest that the developers are fluent English speakers, Raff said. Malware writers tend to use words in their own language in the code, especially when they create custom tools like this one, he said.
A little over 50 percent of the infected systems run Windows XP, 17 percent run Windows Home Server, 9 percent run Windows Server 2003 and 7 percent run Windows 7.