A new cyber attack campaign has come to light, targeting Windows PCs with GHOSTPULSE malware using deceptive MSIX Windows app package files. These attackers are leveraging MSIX, a format used by developers to package and distribute Windows applications, which often requires access to code signing certificates, indicating the involvement of well-funded groups. The attackers use various enticing methods to trick potential victims into downloading these malicious MSIX packages, including compromised websites, SEO poisoning, and malvertising.
Upon launching the MSIX file, users are prompted to click the “Install” button, which initiates the stealthy download of GHOSTPULSE from a remote server via a PowerShell script. This infection process unfolds in multiple stages. Initially, a TAR archive file is used, containing an executable that pretends to be the Oracle VM VirtualBox service (VBoxSVC.exe).
However, it’s actually a legitimate binary bundled with Notepad++ (gup.exe). Additionally, the archive includes handoff.wav and a trojanized version of libcurl.dll, exploiting gup.exe’s vulnerability to DLL side-loading.
To avoid detection by file-based AV and ML scanning, the attackers use PowerShell to execute VBoxSVC.exe, which side-loads the malicious DLL libcurl.dll from the current directory. This method minimizes the on-disk footprint of encrypted malicious code. The tampered DLL then proceeds by parsing handoff.wav, which contains an encrypted payload decoded and executed via mshtml.dll, a technique known as module stomping, ultimately loading GHOSTPULSE.
This malware acts as a loader, employing process doppelgänging to initiate the final malware, which includes SectopRAT, Rhadamanthys, Vidar, Lumma, and NetSupport RAT, posing a significant threat to Windows users.