Ukraine Phishing Campaign (Trojan) – Malware

Overview

On August 12, 2024, Ukraine’s government computer emergency response team, CERT-UA, raised an alarming cybersecurity warning regarding a widespread phishing campaign that has been targeting Ukrainian government entities and local authorities. This campaign, which appears to be an attempt to gain unauthorized access to sensitive government systems, involves emails masquerading as communications from the Security Service of Ukraine (SSU). The emails contain a link leading to a malicious file named “Documents.zip,” which, when opened, triggers the download and execution of a Remote Access Trojan (RAT) known as ANONVNC, a modified version of the MESHAGENT malware.

Targets

Individuals

Information

Public Administration

How they operate

At the core of this phishing campaign is a social engineering technique that preys on the trust of Ukrainian government personnel. The malicious email, appearing to be sent from an official SSU address, entices recipients to click on a link. This link directs the user to a cloud storage service, where they are prompted to download a compressed file named “Documents.zip.” This file, once opened, reveals an MSI file (e.g., “Scan_docs#40562153.msi”), which is executed on the target machine. The MSI installer contains the malicious payload, which, when run, installs ANONVNC (MESHAGENT) malware on the system.

ANONVNC, like its precursor MESHAGENT, is a remote access tool that facilitates hidden, unauthorized access to compromised machines. It is capable of creating a secure, persistent backdoor into infected systems, allowing attackers to monitor and control the device remotely. Upon execution, the malware generates a configuration file formatted similarly to MESHAGENT, suggesting that the threat actors may have borrowed or modified open-source code available on GitHub. The configuration file allows the malware to establish communication with the attacker’s command-and-control (C2) servers, typically hosted on domains like “hiddenvnc.com” and “anonvnc.com.”

Once the malware is installed, it can execute a variety of functions to maintain persistence on the system. It drops malicious executables into critical system directories, such as the Start Menu and Program Files, ensuring that the malware is executed every time the system is rebooted. For example, the malware may place a file named “32x.exe” in the “%PROGRAMDATA%\Microsoft\Windows\Start Menu\Programs\Startup” folder, ensuring it is launched on system startup. Furthermore, ANONVNC has the ability to hide its presence by using legitimate-looking file names and creating decoy processes, making it difficult for standard antivirus or endpoint protection software to detect.

The threat actors behind this campaign appear to have gone to great lengths to obscure their operations, utilizing cloud-based file hosting services like pCloud to distribute the malware and using domains registered under anonymous services like Cloudflare to hide their true identities. This tactic complicates the detection of the malicious infrastructure, as legitimate cloud services and trusted domain providers are frequently used to mask the origin of the attack. The malware’s communication with its C2 servers over encrypted channels (such as HTTPS) further adds to the complexity of detection, making it more difficult for traditional network monitoring systems to identify and block the malicious traffic.

In addition to the ability to maintain persistence and remote access, ANONVNC allows attackers to exfiltrate data from infected systems. This can include sensitive documents, credentials, or other critical government information. The malware’s covert nature and ability to bypass traditional security mechanisms underscore the growing threat of advanced persistent threats (APT), particularly in conflict zones like Ukraine, where state-sponsored cyberattacks are a frequent concern.

References:

• UAC-0198: Mass distribution of ANONVNC (MESHAGENT) among Ukrainian government organizations (CERT-UA#10647)