Parent PID Spoofing (T1134.004)

Description

Adversaries may spoof the parent process identifier (PPID) of a new process to evade process-monitoring defenses or to elevate privileges. New processes are typically spawned directly from their parent, or calling, process unless explicitly specified. One way of explicitly assigning the PPID of a new process is via the CreateProcess API call, which supports a parameter that defines the PPID to use.(Citation: DidierStevens SelectMyParent Nov 2009) This functionality is used by Windows features such as User Account Control (UAC) to correctly set the PPID after a requested elevated process is spawned by SYSTEM (typically via svchost.exe or consent.exe) rather than the current user context.(Citation: Microsoft UAC Nov 2018)

Adversaries may abuse these mechanisms to evade defenses, such as those blocking processes spawning directly from Office documents, and analysis targeting unusual/potentially malicious parent-child process relationships, such as spoofing the PPID of PowerShell/Rundll32 to be explorer.exe rather than an Office document delivered as part of Spearphishing Attachment.(Citation: CounterCept PPID Spoofing Dec 2018) This spoofing could be executed via Visual Basic within a malicious Office document or any code that can perform Native API.(Citation: CTD PPID Spoofing Macro Mar 2019)(Citation: CounterCept PPID Spoofing Dec 2018)

Explicitly assigning the PPID may also enable elevated privileges given appropriate access rights to the parent process. For example, an adversary in a privileged user context (i.e. administrator) may spawn a new process and assign the parent as a process running as SYSTEM (such as lsass.exe), causing the new process to be elevated via the inherited access token.(Citation: XPNSec PPID Nov 2017)