Malware authors developed these Tools with two different features. BalkanRAT, a remote access trojan that controls the compromised computer remotely via a graphical interface and the BalkanDoor performing the same operation using the command-line interface.
Based on the telemetry data that learned by ESET researchers, Balkans campaign spreading these tools since 2016 to various countries Croatia, Serbia, Montenegro, and Bosnia and Herzegovina and very recently the campaign detection on July 2019.
Threat actors using malicious with a weaponized file attachment, links, decoy PDFs as a spreading mechanism and plant both tools in targeted victims computer to gain the complete control of it.
Both tools are digitally signed with various certificates, and it runs as a Windows service that helps to unlock the Windows logon screen remotely and take over of the highest privilege of the infected system.
Infection Process Balkans Campaign
A malspam emails distributed with a link that posed a legitimate website of official institutions and Prompt to drop a malicious file.
A dropped malicious file that linked to PDF executable which is a WinRAR self-extractor and it acts as a legitimate PDF to fool the victims.
Once it executed, the malicious PDF unpack its content and silently execute either BalkanRAT or BalkanDoor.
A very recent BalkanDoor that detected in this year distributed as an ACE archive that specially crafted to exploit the WinRAR ACE vulnerability CVE-2018-20250.
Attacker mostly deploys both tools in the same target system, through which, an attack control the system via both graphical interface and command-line.
According to ESET research, The attacker detects that the victim has their screen locked and thus, most probably, is not using the computer (either via BalkanDoor sending screenshot showing that computer is locked, or via the View Only mode of BalkanRAT). Via the BalkanDoor backdoor, the attacker sends a backdoor command to unlock the screen… and using BalkanRAT, they can do whatever they want on the computer.
There is no exfiltration channel found in BalkanDoor backdoor tool, attackers would need an exfiltration channel for uploading the collected data or they would manually backup the to send it to the attacker.
BalkanDoor – Backdoor
- Simple backdoor with a small number of commands to the remote shell, take a screenshot
- Perform automatic tasks on victims computer and control several computers at once.
- BalkanDoor let the computer connects to a C&C server, identifying itself by the computer name and requesting the commands
- Connects via both HTTP or HTTPS protocol
- Performing repeated connecting attempt via proxy If the connection is not successful.
- it capable of Unlocks the screen, Creates a remote shell and redirects its input/output to the specified IP address and passwordless screen-unlocking.
BalkanRAT – Remote Access Trojan
- Most powerful and complex compared than BalkanDoor.
- Deploy a copy of the Remote Utility software is an ultimate goal.
- IT used for remote access to a computer or for remote administration
- The dropper opens the PDF file so as not to arouse suspicion of the user.
- The core component acts as a keylogger.
- Since BalkanRAT misuses genuine Remote Utilities, communication seems to be legitimate.
“Both BalkanRAT and BalkanDoor have some interesting tricks up their sleeves and each of them separately pose a significant risk to the victims. If used together as a toolset, they make an even more powerful weapon – the more the campaign we have discovered targets accounting, a function that is critical for organizations.” ESET said.
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