ESET researchers discovered and analyzed a malicious campaign in progress, which distributes a backdoor cuts via torrents, using Korean TV content (movies, shows) and often games as bait.
The backdoor has spread through South Korean torrent sites and China. The malware allows the attacker to connect the compromised computer to a botnet and control it remotely.
This malware is a modified version of GoBot2, a publicly available backdoor. The source code modifications mainly concern escape techniques specifically for use in South Korea. As the campaign clearly targets that country, ESET has named GoBotKR the specific version of Win64 / GoBot2. According to ESET telemetry, GoBotKR is active by 2018. South Korea is the country with the most attacks (80% of detections), followed by China (10%) and Taiwan (5%).
“Οι κυβερνοεγκληματίες που βρίσκονται πίσω από αυτή την εκστρατεία προσπαθούν να ξεγελάσουν τους χρήστες να εκτελέσουν το κακόβουλο λογισμικό με το να τοποθετούν στο περιεχόμενο των torrents παγίδες με κακόβουλα αρχεία που έχουν παραπλανητικά ονόματα αρχείων, επεκτάσεις και icons,” says ESET researcher Zuzana Hromcova, who analyzed the malware.
No malicious action will occur directly by opening the MP4 file. The trap here is that the MP4 file is often hidden in a different directory, and users may first encounter the malicious file that mimics it.
According to ESET, malware is not technically complex. However, the cybercriminals behind GoBotKR are building a network of bots, which can then be used to carry out various types of DDoS attacks. Therefore, after running, GoBotKR first collects system information about the affected computer, such as network settings, operating system release information, CPU, and GPU.
Specifically, it collects a list of installed antivirus products. This information is sent to a C&C server, which helps intruders determine which bots can be used in the respective attacks. "All the C&C servers found through the malware samples analyzed were found to be hosted in South Korea and registered by the same person," Hromcova explained in her research.
The bot has many features, such as allowing abuse of the compromised computer, or enabling botnet operators to further control or extend the botnet. It also allows to avoid detection and concealment by the user.
Among other supported commands are the ability to direct a DDoS attack to specific victims, copy the malware to attached removable media or public cloud storage service folders (Dropbox, OneDrive, Google Drive), as well as embedding torrents with the malicious file as a means to further expand the botnet.
Από πλευράς έρευνας, το GoBotKR παρουσιάζει ιδιαίτερο ενδιαφέρον για τις τεχνικές διαφυγής του, οι οποίες προσαρμόστηκαν για να στοχεύσουν τη Νότια Κορέα. Συγκεκριμένα, το κακόβουλο λογισμικό σαρώνει διαδικασίες που εκτελούνται στο παραβιασμένο system προκειμένου να ανιχνεύσει συγκεκριμένα προϊόντα antivirus, μεταξύ των οποίων συγκαταλέγονται τα προϊόντα μιας εταιρείας λύσεων ασφάλειας της Νότιας Κορέας.
If any of the products are found, they are terminated. Another escape technique detects system-running analytics tools, again targeting the same South Korean security firm. In the third avoidance technique, the intruders misused legitimate South Korean electronic platforms to determine the victim's IP address.
"Overall, the modifications show us that the attackers are adapting the malware to a specific audience while also making extra efforts to prevent it from being detected," Hromcova concludes.
More details about GoBotKR and its features can be found in the ESET blogpost «Malicious campaign targets South Korean users with backdoor-laced torrents"At WeLiveSecurity.com.
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