Security experts have discovered a family of data-stealing trojans that have burrowed into automatic teller machines in Eastern Europe over the past 18 months.
The malware logs the magnetic-stripe data and personal identification number of cards used at an infected machine and provides an intuitive interface for retrieving the information using the ATM's receipt printer, according to analysts from SpiderLabs, the research arm of security firm Trustwave. Since late 2007 or so, there have been at least 16 updates to the software, an indication that the authors are working hard to perfect their tool.
"They're following more of a rapid development lifecycle," Nicholas Percoco, vice president and head of SpiderLabs, told The Register. "They're seeing what works and putting out new versions."
SpiderLabs researchers delved into four of the more recent versions and what they found was a highly capable family malware written with professional standards. Once installed, it monitors the ATM's transaction message queue for track 2 data stored on inserted cards. If it contains data belonging to a banking customer, it logs it, along with the PIN code that was entered.
The software also works with controller cards that allow the attackers to operate infected machines. When such a card is inserted, the ATM's display shows a window offering 10 command options that can be selected using the keypad. Options include the ability to print collected data, restore log files to the condition prior to the malware installation, and uninstall the malware altogether.
A secondary menu also allows the person to force the machine to dispense all its cash. There is also documentation for another feature that would upload intercepted card data to a chip on the controller card, but that capability doesn't seem to work yet. Controller cards include both master and single function. The former is presumably for people higher up in the organization while the latter would be used by mules who are not fully trusted.
The findings build on a report issued in March by Sophos that documented card-sniffing trojans that targeted ATMs made by Diebold. The ATM manufacturer said several suspects had been apprehended following an incident "isolated in Russia" in which attempts were made to use the malware.
SpiderLabs' Percoco said he didn't know if the malware his researchers studied was tied to the Sophos report. Both malicious programs can be installed only by people with physical access to the machines, making some level of insider cooperation necessary. But unlike the Sophos report, SpiderLabs said the software targeted ATMs made by multiple vendors, though Percoco declined to say which ones. The SpiderLabs report said only that the targeted ATMs ran on the Windows XP operating system.
"These are systems that are connected to financial networks that are literally sitting out in the open, and they are vulnerable," Percoco said. "All these systems are unattended, or most of them are. You often walk by when they're being serviced."A PDF containing additional technical details is available here.