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New Custom RAT Hits Targets in East Asia

A newly discovered custom remote access Trojan (RAT) has been used in attacks on personnel or organizations related to South Korea and the video gaming industry, Palo Alto Networks reveals.

Called UBoatRAT, and distributed through Google Drive links, the RAT obtains its command and control (C&C) address from GitHub and uses Microsoft Windows Background Intelligent Transfer Service (BITS) to maintain persistence.

The malware was initially spotted in May 2017, when it was a simple HTTP backdoor using a public blog service in Hong Kong and a compromised web server in Japan for C&C. Since then, the developer added various new features to the threat and released updated versions during summer. The analyzed attacks were observed in September.

While the exact targets aren’t clear at the moment, Palo Alto Networks believes they are related to Korea or the video games industry, due to the fact that Korean-language game titles, Korea-based game company names, and some words used in the video games business were used for delivery.

UBoatRAT, the security researchers say, performs malicious activities on the compromised machine only when joining an Active Directory Domain, which means that most home user systems won’t be impacted, since they are not part of a domain.

The malware is delivered through a ZIP archive hosted on Google Drive and containing a malicious executable file disguised as a folder or a Microsoft Excel spread sheet. The latest variants of the malware masquerade as Microsoft Word document files.

Once running on a compromised machine, the threat checks for virtualization software such as VMWare, VirtualBox, QEmu, and then attempts to obtain Domain Name from network parameters. If it detects a virtual environment or fails to get the domain name, it displays a fake error message and quits.

Otherwise, UBoatRAT copies itself to C:\programdata\svchost.exe, and creates and executes C:\programdata\init.bat, after which it displays a specific message and quits.

The malware uses the Microsoft Windows Background Intelligent Transfer Service (BITS) – a service for transferring files between machines – for persistence. BITS jobs can be created and monitored via the Bitsadmin.exe command-line tool, which offers an option to execute a program when the job finishes transferring data or is in error, and UBoatRAT uses this option to run on the system even after reboot.

The C&C address and the destination port are hidden in a file hosted on GitHub, and the malware accesses the file using a specific URL. A custom C&C protocol is employed for communication with the attacker’s server.

Backdoor commands received from the attacker include: alive (checks if the RAT is alive), online (keeps the RAT online), upfile (uploads file to compromised machine), downfile (downloads file from compromised machine), exec (executes process with UAC Bypass using Eventvwr.exe and Registry Hijacking), start (starts CMD shell), curl (downloads file from specified URL), pslist (lists running processes), and pskill (terminates specified process).

Palo Alto researchers have identified fourteen samples of UBoatRAT, as well as one downloader associated with the attacks. The researchers also associated the malware with the GitHub account ‘elsa999’ and determined that the author has been frequently updating repositories since July.

“Though the latest version of UBoatRAT was released in September, we have seen multiple updates in elsa999 accounts on GitHub in October. The author seems to be vigorously developing or testing the threat. We will continue to monitor this activity for updates,” Palo Alto concludes.

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