The US government has put out an alert warning retailers about a new family of malware, dubbed Backoff, targeting point-of-sale systems.
Crooks are tapping publicly available tools to find businesses that use remote desktop applications and then brute-forcing access by taking advantage of weak passwords, says the US Computer Emergency Response Team (US-Cert).
Once they have access to administrator accounts, the attackers can then deploy the POS malware and steal payment data and other personal information via an encrypted Post request.
Working with the Secret Service and Trustwave Spiderlabs, US-Cert has identified three primary variants of the malware, which were first spotted last October and are all still operating.
The software's capabilities include scraping memory for track data, logging keystrokes, command and control communication, and injecting malicious stub into explorer.exe.
Backoff has been found in at least three separate forensic investigations into POS data breaches and is currently almost never picked up by anti-virus engines, warns US-Cert.
Remote access-based attacks on POS systems have shot up the agenda of retailers since last year's Target breach, which saw thieves use a vendor's credentials to infect POS devices with malware and steal the details of around 40 million customer cards.
US-Cert offers retailers advice on dealing with the threat in its alert.