The ongoing migration of the US payment system to smartcards based on the EMV standard is expected to cut down certain types of credit and debit card fraud in a big way. But that’s not stopping attackers from rushing in to take advantage of those who haven’t made the switch to the new standard yet.

Designed to help them on that mission is a new version of CenterPOS, a malware tool that was released last September to steal credit and debit card data from point-of-sale (POS) systems.

Security firm FireEye, which discovered the updated version of CenterPOS recently, described it as being functionally very similar to the original version but supporting certain features that make it more dangerous.

One of the key differences in the new version of CenterPOS is its ability to create a configuration file for storing information on the command-and-control server it communicates with, right from the payload itself.

When CenterPOS is executed, the first thing it does is to search for a configuration file that contains the C&C information. If it doesn’t find a configuration file, the malware is designed to open a dialog box that prompts for a password, FireEye said.

“If the correct password is entered, a dialog box will appear that allows an operator to enter CnC information, as well as a password used to encrypt the configuration file,” the company said in its alert.

The malware payload contains the functionality to create a configuration file, says Nart Villeneuve, principal threat intelligence analyst at FireEye in comments to Dark Reading. The reason it is important is because it allows malware operators to update command-and-control information more easily and as needed.

“This is uncommon. Usually, malware tools have a separate component called a 'builder' that is used to create a payload that contains the CnC information,” he says. The capability is useful in situations where a security tool might block access to the CnC server and the attacks need to configure a new one to which the malware can connect, he says.

A configuration file is a handy mechanism for storing CnC data, according to Villeneuve. Simply by deleting the configuration file after an attack, a threat actor can wipe clean all information on the location of the server with which the malware was communicating. Maintaining a separate configuration file also ensures that command-and-control data is not compromised if the malware executable itself is detected, quarantined, and analyzed. “This makes it hard to track the activities of specific threat groups, Villeneuve says.

CenterPOS uses what FireEye described as a “smart scan” mode and a normal mode to look for credit and debit card data being handled by a compromised system. It encrypts all data that matches the description of what it is looking for using TripleDES encryption using an encryption key provided in the configuration file. All data collected is then sent to a server controlled by operators of the malware.

Malicious software like CenterPOS do not work with EMV transactions, says Villeneuve. That’s because card data is stored in a microchip on the card that generates a unique code for every transaction, making it pointless for attackers to steal data at the POS.

Though the deadline to cut over to EMV smartcards and terminals ended in October, many retailers and merchants that accept payment cards are only still in the process of making the switch. Cybercriminals are anxious to use the closing window of opportunity -- resulting in a surge in attacks against POS systems.

"The cybercriminals are inspired by the successful, large breaches in the news and know that memory-scraping techniques will no longer work after the shift to chip-and-PIN,” Villeneuve said. But it will take some time for the shift to be complete. “So they are trying to take advantage of POS malware while they still can.”