Thousands of compromised computers are actively trying to break into point-of-sale (PoS) systems using brute-force techniques to guess remote administration credentials.
The computers are part of a botnet, dubbed BrutPOS by researchers from security firm FireEye, that has been active since at least February. The botnet scans attacker-specified IP address ranges for systems that accept Remote Desktop Protocol (port 3389) connections.
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When an RDP service is identified, the BrutPOS malware attempts to log in with user names and passwords from a predefined list.
"Some of the usernames and passwords indicate that the attackers are looking for specific brands of PoS systems such as Micros," the FireEye researchers said Wednesday in a blog post.
Micros Systems is based in Columbia, Maryland, and provides software applications, services, and hardware systems, including PoS terminals, to the hospitality and retail industries.
If the BrutPOS malware successfully guesses the remote access credentials of an RDP-enabled system, it sends the information back to a command-and-control server. Attackers then use the information to determine whether the system is a PoS terminal and, if it is, to install a malware program that's designed to extract payment card details from the memory of applications running on it.
This kind of memory monitoring program is known as a RAM scraper and has increasingly been used in attacks against PoS systems over the past year. A data breach last year at Target that led to the compromise of 40 million payment cards resulted from the retailer's PoS terminals being infected by RAM scraping malware.
Researchers from cyberthreat intelligence firm IntelCrawler have also monitored the BrutPOS malware, which they believe appeared in the cybercriminal underground in May as a project called @-Brt. According to them, it doesn't only target RDP, but other remote administration protocols like VNC and PCAnywhere as well.
FireEye has identified a total of five BrutPOS command-and-control servers, two of which are still online. The two remaining servers are located in Russia and were set up in late May and early June, respectively.
Data collected from these servers suggests that the botnet is made up of 5,622 compromised computers from 119 countries. The researchers identified 60 RDP-enabled systems -- most likely PoS terminals -- that have been compromised, 51 of which are based in the United States.
"The most common username was 'administrator' (36) and the most common passwords were 'pos' (12) and 'Password1' (12)," the FireEye researchers said.
According to IntelCrawler's data, other remote access passwords frequently used on the compromised systems were aloha12345, micros, pos12345, posadmin, and javapos.
"While there is insufficient information to determine attribution, there is some information which indicates that the attackers are in Eastern Europe, probably Russia or Ukraine," the FireEye researchers said.
In recent years PoS systems have become a significant target for cybercriminals. Security firm Trustwave recently reported that over a third of data breaches the company investigated last year involved intrusions into PoS terminals. Weak passwords, especially those for VPNs, SSH, and remote desktop connections remained a leading cause of breaches, the company said.
Brute-forced remote access connections and stolen credentials were the primary vectors for PoS intrusions in 2013, Verizon said in its own data breach investigations report in April.