Hackers have innovated their tactics by utilizing weaponized Virtual Hard Disk (VHD) files to propagate the Remcos Remote Access Trojan (RAT). Originally introduced as a legitimate remote control tool by BreakingSecurity in 2016, Remcos has since been exploited by cybercriminals for nefarious purposes. Recent findings from K7SecurityLabs have shed light on the alarming trend of distributing Remcos RAT through .vhd files, showcasing a significant evolution in cyberattack strategies.
The discovery of weaponized VHD files as a delivery mechanism for Remcos RAT highlights the attackers’ increasing sophistication. Analysis of these files reveals intricate operations, including the execution of PowerShell scripts disguised within a MacOSX.ps1 file, demonstrating a multifaceted approach to malware deployment. Notably, the utilization of advanced obfuscation techniques, such as AMSI Bypass and base64 encoding within PNG files, underscores the attackers’ efforts to evade detection and amplify the effectiveness of their malicious payloads.
The complexity of the attack is further elucidated by the multifunctional nature of the MacOSX.ps1 script, which orchestrates the download and execution of additional malicious payloads. These payloads, encoded within various file formats, ultimately lead to the injection of the Remcos RAT payload into system processes, enabling persistent access and control for the attackers. The Remcos payload, armed with an encrypted configuration block, empowers threat actors to conduct a wide range of malicious activities, including keystroke logging, audio capture, and communication with Command and Control (C2) servers.
