Windows AppX Deployment Package Installation Success: endpointEndpoint2025-08-05version:1
This analytic detects successful MSIX/AppX package installations on Windows systems by monitoring EventID 854 in the Microsoft-Windows-AppXDeployment-Server/Operational log. This event is generated when an MSIX/AppX package has been successfully installed on a system. While most package installations are legitimate, monitoring these events can help identify unauthorized or suspicious package installations, especially when correlated with other events such as unsigned package installations (EventID 603 with Flags=8388608) or full trust package installations (EventID 400 with HasFullTrust=true).
Windows MSIX Package Interaction: endpointEndpoint2025-08-05version:1
This hunting query detects user interactions with MSIX packages by monitoring EventCode 171 in the Microsoft-Windows-AppXPackaging/Operational logs. These events are generated when a user clicks on or attempts to interact with an MSIX package, even if the package is not fully installed. This information can be valuable for security teams to identify what MSIX packages users are attempting to open in their environment, which may help detect malicious MSIX packages before they're fully installed. Monitoring these interactions can provide early warning of potential MSIX package abuse, which has been leveraged by threat actors such as FIN7, Zloader (Storm-0569), and FakeBat (Storm-1113).
Windows Developer-Signed MSIX Package Installation: endpointEndpoint2025-08-05version:1
This detection identifies the installation of developer-signed MSIX packages that lack Microsoft Store signatures. All malicious MSIX packages observed in recent threat campaigns (including those from FIN7, Zloader/Storm-0569, and FakeBat/Storm-1113) were developer-signed rather than Microsoft Store signed. Microsoft Store apps have specific publisher IDs containing '8wekyb3d8bbwe' or 'cw5n1h2txyewy', while developer-signed packages lack these identifiers. This detection focuses on EventID 855 from the Microsoft-Windows-AppXDeployment-Server/Operational logs, which indicates a completed package installation.
Windows Advanced Installer MSIX with AI_STUBS Execution: endpointEndpoint2025-08-05version:1
The following analytic identifies the execution of Advanced Installer MSIX Package Support Framework (PSF) components, specifically the AI_STUBS executables with the original filename 'popupwrapper.exe'. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process paths and original filenames. This activity is significant as adversaries have been observed packaging malicious content within MSIX files built with Advanced Installer to bypass security controls. These AI_STUBS executables (with original filename 'popupwrapper.exe') are hallmark artifacts of potentially malicious MSIX packages. If confirmed malicious, this could allow attackers to execute arbitrary code, establish persistence, or deliver malware while evading traditional detection mechanisms.
Windows AppX Deployment Full Trust Package Installation: endpointEndpoint2025-08-05version:1
The following analytic detects the installation of MSIX/AppX packages with full trust privileges. This detection leverages Windows event logs from the AppXDeployment-Server, specifically focusing on EventCode 400 which indicates a package deployment operation. Full trust packages are significant as they run with elevated privileges outside the normal AppX container restrictions, allowing them to access system resources that regular AppX packages cannot. Adversaries have been observed leveraging full trust MSIX packages to deliver malware, as documented in recent threat intelligence reports. If confirmed malicious, these packages could allow attackers to execute arbitrary code with elevated privileges, establish persistence, or deliver malware while evading traditional detection mechanisms.
Windows PowerShell Script From WindowsApps Directory: endpointEndpoint2025-08-05version:1
The following analytic identifies the execution of PowerShell scripts from the WindowsApps directory, which is a common technique used in malicious MSIX package execution. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process command lines and parent process paths. This activity is significant as adversaries have been observed using MSIX packages with embedded PowerShell scripts (particularly StartingScriptWrapper.ps1) to execute malicious code. If confirmed malicious, this could allow attackers to execute arbitrary code, establish persistence, or deliver malware while evading traditional detection mechanisms.
Windows AppX Deployment Unsigned Package Installation: endpointEndpoint2025-08-05version:1
The following analytic detects attempts to install unsigned MSIX/AppX packages using the -AllowUnsigned parameter. This detection leverages Windows event logs from the AppXDeployment-Server, specifically focusing on EventID 603 which indicates the start of a deployment operation with specific deployment flags. The flag value 8388608 corresponds to the -AllowUnsigned option in PowerShell's Add-AppxPackage cmdlet. This activity is significant as adversaries have been observed leveraging unsigned MSIX packages to deliver malware, bypassing signature verification that would normally protect users from malicious packages. If confirmed malicious, this could allow attackers to execute arbitrary code, establish persistence, or deliver malware while evading traditional detection mechanisms.
Windows PowerShell MSIX Package Installation: endpointEndpoint2025-08-05version:1
The following analytic detects the execution of PowerShell commands to install unsigned AppX packages using Add-AppxPackage or Add-AppPackage cmdlets with the -AllowUnsigned flag. This detection leverages PowerShell Script Block Logging (EventCode=4104) to capture the full command content. This activity is significant as adversaries may use unsigned AppX packages to install malicious applications, bypass security controls, or establish persistence. If confirmed malicious, this could allow attackers to install unauthorized applications that may contain malware, backdoors, or other malicious components.
