Process Injection: Process Hollowing

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.[1][2]

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.

ID: T1055.012
Sub-technique of:  T1055
Platforms: Windows
Permissions Required: User
Defense Bypassed: Anti-virus, Application control
Version: 1.3
Created: 14 January 2020
Last Modified: 11 August 2023

Procedure Examples

ID Name Description
S0331 Agent Tesla

Agent Tesla has used process hollowing to create and manipulate processes through sections of unmapped memory by reallocating that space with its malicious code.[3]

S0373 Astaroth

Astaroth can create a new process in a suspended state from a targeted legitimate process in order to unmap its memory and replace it with malicious code.[4][5]

S0344 Azorult

Azorult can decrypt the payload into memory, create a new suspended process of itself, then inject a decrypted payload to the new process and resume new process execution.[6]


BADNEWS has a command to download an .exe and use process hollowing to inject it into a new process.[7][8]

S0234 Bandook

Bandook has been launched by starting iexplore.exe and replacing it with Bandook's payload.[9][10][11]

S0534 Bazar

Bazar can inject into a target process including Svchost, Explorer, and cmd using process hollowing.[12][13]


BBSRAT has been seen loaded into msiexec.exe through process hollowing to hide its execution.[14]

S0660 Clambling

Clambling can execute binaries through process hollowing.[15]

S0154 Cobalt Strike

Cobalt Strike can use process hollowing for execution.[16][17]

S0354 Denis

Denis performed process hollowing through the API calls CreateRemoteThread, ResumeThread, and Wow64SetThreadContext.[18]

S0567 Dtrack

Dtrack has used process hollowing shellcode to target a predefined list of processes from %SYSTEM32%.[19]

S0038 Duqu

Duqu is capable of loading executable code via process hollowing.[20]

G0078 Gorgon Group

Gorgon Group malware can use process hollowing to inject one of its trojans into another process.[21]

S0189 ISMInjector

ISMInjector hollows out a newly created process RegASM.exe and injects its payload into the hollowed process.[22]

G0094 Kimsuky

Kimsuky has used a file injector DLL to spawn a benign process on the victim's system and inject the malicious payload into it via process hollowing.[23]

S0447 Lokibot

Lokibot has used process hollowing to inject itself into legitimate Windows process.[24][25]

G0045 menuPass

menuPass has used process hollowing in iexplore.exe to load the RedLeaves implant.[26]


The NETWIRE payload has been injected into benign Microsoft executables via process hollowing.[27][28]

S0229 Orz

Some Orz versions have an embedded DLL known as MockDll that uses process hollowing and Regsvr32 to execute another payload.[29]

G0040 Patchwork

A Patchwork payload uses process hollowing to hide the UAC bypass vulnerability exploitation inside svchost.exe.[30]

S0650 QakBot

QakBot can use process hollowing to execute its main payload.[31]

S0662 RCSession

RCSession can launch itself from a hollowed svchost.exe process.[32][15][33]

S1018 Saint Bot

The Saint Bot loader has used API calls to spawn MSBuild.exe in a suspended state before injecting the decrypted Saint Bot binary into it.[34]

S0226 Smoke Loader

Smoke Loader spawns a new copy of c:\windows\syswow64\explorer.exe and then replaces the executable code in memory with malware.[35][36]

S1086 Snip3

Snip3 can use RunPE to execute malicious payloads within a hollowed Windows process.[37][38]

G1018 TA2541

TA2541 has used process hollowing to execute CyberGate malware.[39]

G0027 Threat Group-3390

A Threat Group-3390 tool can spawn svchost.exe and inject the payload into that process.[40][41]

S0266 TrickBot

TrickBot injects into the svchost.exe process.[42][43][44][45]

S0386 Ursnif

Ursnif has used process hollowing to inject into child processes.[46]

S0689 WhisperGate

WhisperGate has the ability to inject its fourth stage into a suspended process created by the legitimate Windows utility InstallUtil.exe.[47][48]

S1065 Woody RAT

Woody RAT can create a suspended notepad process and write shellcode to delete a file into the suspended process using NtWriteVirtualMemory.[49]


ID Mitigation Description
M1040 Behavior Prevention on Endpoint

Some endpoint security solutions can be configured to block some types of process injection based on common sequences of behavior that occur during the injection process.


ID Data Source Data Component Detects
DS0009 Process OS API Execution

Monitoring Windows API calls indicative of the various types of code injection may generate a significant amount of data and may not be directly useful for defense unless collected under specific circumstances for known bad sequences of calls, since benign use of API functions may be common and difficult to distinguish from malicious behavior. Windows API calls such as CreateRemoteThread, SuspendThread/SetThreadContext/ResumeThread, and those that can be used to modify memory within another process, such as VirtualAllocEx/WriteProcessMemory, may be used for this technique.[2]

Process Access

Monitor for processes being viewed that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses.

Process Creation

Monitor for newly executed processes that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses. 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.

Analytic 1 - Processes Started From Irregular Parents

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"))

Process Modification

Monitor for changes made to processes that may inject malicious code into suspended and hollowed processes in order to evade process-based defenses.


  1. Leitch, J. (n.d.). Process Hollowing. Retrieved November 12, 2014.
  2. Hosseini, A. (2017, July 18). Ten Process Injection Techniques: A Technical Survey Of Common And Trending Process Injection Techniques. Retrieved December 7, 2017.
  3. Walter, J. (2020, August 10). Agent Tesla | Old RAT Uses New Tricks to Stay on Top. Retrieved December 11, 2020.
  5. GReAT. (2020, July 14). The Tetrade: Brazilian banking malware goes global. Retrieved November 9, 2020.
  6. Yan, T., et al. (2018, November 21). New Wine in Old Bottle: New Azorult Variant Found in FindMyName Campaign using Fallout Exploit Kit. Retrieved November 29, 2018.
  7. Settle, A., et al. (2016, August 8). MONSOON - Analysis Of An APT Campaign. Retrieved September 22, 2016.
  8. Lunghi, D., et al. (2017, December). Untangling the Patchwork Cyberespionage Group. Retrieved July 10, 2018.
  9. Blaich, A., et al. (2018, January 18). Dark Caracal: Cyber-espionage at a Global Scale. Retrieved April 11, 2018.
  10. Galperin, E., Et al.. (2016, August). I Got a Letter From the Government the Other Day.... Retrieved April 25, 2018.
  11. Check Point. (2020, November 26). Bandook: Signed & Delivered. Retrieved May 31, 2021.
  12. Cybereason Nocturnus. (2020, July 16). A BAZAR OF TRICKS: FOLLOWING TEAM9’S DEVELOPMENT CYCLES. Retrieved November 18, 2020.
  13. Pantazopoulos, N. (2020, June 2). In-depth analysis of the new Team9 malware family. Retrieved December 1, 2020.
  14. Lee, B. Grunzweig, J. (2015, December 22). BBSRAT Attacks Targeting Russian Organizations Linked to Roaming Tiger. Retrieved August 19, 2016.
  15. Lunghi, D. et al. (2020, February). Uncovering DRBControl. Retrieved November 12, 2021.
  16. Cobalt Strike. (2017, December 8). Tactics, Techniques, and Procedures. Retrieved December 20, 2017.
  17. Strategic Cyber LLC. (2020, November 5). Cobalt Strike: Advanced Threat Tactics for Penetration Testers. Retrieved April 13, 2021.
  18. Dahan, A. (2017). Operation Cobalt Kitty. Retrieved December 27, 2018.
  19. Konstantin Zykov. (2019, September 23). Hello! My name is Dtrack. Retrieved January 20, 2021.
  20. Symantec Security Response. (2011, November). W32.Duqu: The precursor to the next Stuxnet. Retrieved September 17, 2015.
  21. Falcone, R., et al. (2018, August 02). The Gorgon Group: Slithering Between Nation State and Cybercrime. Retrieved August 7, 2018.
  22. Falcone, R. and Lee, B. (2017, October 9). OilRig Group Steps Up Attacks with New Delivery Documents and New Injector Trojan. Retrieved January 8, 2018.
  23. An, J and Malhotra, A. (2021, November 10). North Korean attackers use malicious blogs to deliver malware to high-profile South Korean targets. Retrieved December 29, 2021.
  24. Hoang, M. (2019, January 31). Malicious Activity Report: Elements of Lokibot Infostealer. Retrieved May 15, 2020.
  25. Muhammad, I., Unterbrink, H.. (2021, January 6). A Deep Dive into Lokibot Infection Chain. Retrieved August 31, 2021.
  1. Accenture Security. (2018, April 23). Hogfish Redleaves Campaign. Retrieved July 2, 2018.
  2. Maniath, S. and Kadam P. (2019, March 19). Dissecting a NETWIRE Phishing Campaign's Usage of Process Hollowing. Retrieved January 7, 2021.
  3. Lambert, T. (2020, January 29). Intro to Netwire. Retrieved January 7, 2021.
  4. Axel F, Pierre T. (2017, October 16). Leviathan: Espionage actor spearphishes maritime and defense targets. Retrieved February 15, 2018.
  5. Cymmetria. (2016). Unveiling Patchwork - The Copy-Paste APT. Retrieved August 3, 2016.
  6. Morrow, D. (2021, April 15). The rise of QakBot. Retrieved September 27, 2021.
  7. Counter Threat Unit Research Team. (2019, December 29). BRONZE PRESIDENT Targets NGOs. Retrieved April 13, 2021.
  8. Global Threat Center, Intelligence Team. (2020, December). APT27 Turns to Ransomware. Retrieved November 12, 2021.
  9. Unit 42. (2022, February 25). Spear Phishing Attacks Target Organizations in Ukraine, Payloads Include the Document Stealer OutSteel and the Downloader SaintBot. Retrieved June 9, 2022.
  10. Hasherezade. (2016, September 12). Smoke Loader – downloader with a smokescreen still alive. Retrieved March 20, 2018.
  11. Windows Defender Research. (2018, March 7). Behavior monitoring combined with machine learning spoils a massive Dofoil coin mining campaign. Retrieved March 20, 2018.
  12. Lorber, N. (2021, May 7). Revealing the Snip3 Crypter, a Highly Evasive RAT Loader. Retrieved September 13, 2023.
  13. Jornet, A. (2021, December 23). Snip3, an investigation into malware. Retrieved September 19, 2023.
  14. Ventura, V. (2021, September 16). Operation Layover: How we tracked an attack on the aviation industry to five years of compromise. Retrieved September 15, 2023.
  15. Pantazopoulos, N., Henry T. (2018, May 18). Emissary Panda – A potential new malicious tool. Retrieved June 25, 2018.
  16. Legezo, D. (2018, June 13). LuckyMouse hits national data center to organize country-level waterholing campaign. Retrieved August 18, 2018.
  17. Salinas, M., Holguin, J. (2017, June). Evolution of Trickbot. Retrieved July 31, 2018.
  18. Antazo, F. (2016, October 31). TSPY_TRICKLOAD.N. Retrieved September 14, 2018.
  19. Pornasdoro, A. (2017, October 12). Trojan:Win32/Totbrick. Retrieved September 14, 2018.
  20. Dahan, A. et al. (2019, December 11). DROPPING ANCHOR: FROM A TRICKBOT INFECTION TO THE DISCOVERY OF THE ANCHOR MALWARE. Retrieved September 10, 2020.
  21. Vaish, A. & Nemes, S. (2017, November 28). Newly Observed Ursnif Variant Employs Malicious TLS Callback Technique to Achieve Process Injection. Retrieved June 5, 2019.
  22. Biasini, N. et al.. (2022, January 21). Ukraine Campaign Delivers Defacement and Wipers, in Continued Escalation. Retrieved March 14, 2022.
  23. Insikt Group. (2020, January 28). WhisperGate Malware Corrupts Computers in Ukraine. Retrieved March 31, 2023.
  24. MalwareBytes Threat Intelligence Team. (2022, August 3). Woody RAT: A new feature-rich malware spotted in the wild. Retrieved December 6, 2022.