Adversaries may abuse SyncAppvPublishingServer.vbs to proxy execution of malicious PowerShell commands. SyncAppvPublishingServer.vbs is a Visual Basic script associated with how Windows virtualizes applications (Microsoft Application Virtualization, or App-V).[1] For example, Windows may render Win32 applications to users as virtual applications, allowing users to launch and interact with them as if they were installed locally.[2][3]
The SyncAppvPublishingServer.vbs script is legitimate, may be signed by Microsoft, and is commonly executed from \System32 through the command line via wscript.exe.[4][5]
Adversaries may abuse SyncAppvPublishingServer.vbs to bypass PowerShell execution restrictions and evade defensive counter measures by "living off the land."[6][4] Proxying execution may function as a trusted/signed alternative to directly invoking powershell.exe.[7]
For example, PowerShell commands may be invoked using:[5]
SyncAppvPublishingServer.vbs "n; {PowerShell}"
| ID | Mitigation | Description |
|---|---|---|
| M1038 | Execution Prevention |
Certain signed scripts that can be used to execute other programs may not be necessary within a given environment. Use application control configured to block execution of these scripts if they are not required for a given system or network to prevent potential misuse by adversaries. |
| ID | Data Source | Data Component | Detects |
|---|---|---|---|
| DS0017 | Command | Command Execution |
Monitor executed commands and arguments for scripts like Syncappvpublishingserver.vbs that may be used to proxy execution of malicious files. |
| DS0009 | Process | Process Creation |
Monitor script processes, such as |
| DS0012 | Script | Script Execution |
Monitor for any attempts to enable scripts running on a system would be considered suspicious. If scripts are not commonly used on a system, but enabled, scripts running out of cycle from patching or other administrator functions are suspicious. Scripts should be captured from the file system when possible to determine their actions and intent. |