Point-of-Sale (PoS) terminals have become an attractive target for hackers over the past year, reflected in the increasing number of RAM-scraping programs that steal payment card information from the memory of such systems.

Last month security researchers from Cisco Systems issued a warning about a new PoS threat dubbed PoSeidon and on Wednesday security blogger Brian Krebs reported that the program has already infected PoS terminals at restaurants, bars and hotels in the U.S.

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Security researchers from Trustwave now warn that during a recent investigation with the U.S. Secret Service, they've uncovered yet another RAM-scraping PoS threat they've named Punkey.

This new malicious program, that has at least three variants, is very similar to another family of PoS malware known as NewPosThings. The similarities suggest the two families are based on the same source code, but Punkey has enough differences to make it unique.

Punkey has versions for both 32-bit and 64-bit Windows-based PoS terminals and in addition to stealing payment card data while it's being processed, it also installs a keylogger to capture what employees type on such systems.

The malware injects itself into the Windows explorer.exe process and creates registry start-up entries to ensure its persistence. It also drops a file called DLLx64.dll which is the keylogger component.

All payment card details and keystrokes captured by the malware are first encrypted with AES (Advanced Encryption Standard) and are then sent back to a command-and-control (C&C) server.

The malware can also download and execute other malicious files, including updates for itself.

"This gives Punkey the ability to run additional tools on the system such as executing additional reconnaissance tools or performing privilege escalation," the Trustwave researchers said in a blog post. "This is a rare feature for POS malware."

Trustwave created a tool that can decrypt Punkey traffic and published it on GitHub. This could help PoS terminal owners identify Punkey traffic on their networks.

In its annual Data Breach Investigations Report released this week, Verizon Enterprise Solutions noted a significant increase in the number of PoS RAM scraping attacks. In fact, PoS intrusions were one of the top three causes for confirmed data breaches last year according to the company.

The trend appears to have continued this year. Between PoSeidon last month and Punkey now, malware researchers also found other PoS malware threats: new variants of NewPosThings and a program called FighterPOS that infected over 100 organizations in Brazil.