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T1055.012 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.12

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.

Item Value
ID T1055.012
Sub-techniques T1055.001, T1055.002, T1055.003, T1055.004, T1055.005, T1055.008, T1055.009, T1055.011, T1055.012, T1055.013, T1055.014, T1055.015
Tactics TA0005, TA0004
Platforms Windows
Permissions required User
Version 1.2
Created 14 January 2020
Last Modified 29 November 2021

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.23
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.2627
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.8
S0128 BADNEWS BADNEWS has a command to download an .exe and use process hollowing to inject it into a new process.3233
S0234 Bandook Bandook has been launched by starting iexplore.exe and replacing it with Bandook‘s payload.567
S0534 Bazar Bazar can inject into a target process including Svchost, Explorer, and cmd using process hollowing.2021
S0127 BBSRAT BBSRAT has been seen loaded into msiexec.exe through process hollowing to hide its execution.16
S0660 Clambling Clambling can execute binaries through process hollowing.40
S0154 Cobalt Strike Cobalt Strike can use process hollowing for execution.1415
S0354 Denis Denis performed process hollowing through the API calls CreateRemoteThread, ResumeThread, and Wow64SetThreadContext.24
S0567 Dtrack Dtrack has used process hollowing shellcode to target a predefined list of processes from %SYSTEM32%.39
S0038 Duqu Duqu is capable of loading executable code via process hollowing.22
G0078 Gorgon Group Gorgon Group malware can use process hollowing to inject one of its trojans into another process.47
S0189 ISMInjector ISMInjector hollows out a newly created process RegASM.exe and injects its payload into the hollowed process.38
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.48
S0447 Lokibot Lokibot has used process hollowing to inject itself into legitimate Windows process.1819
G0045 menuPass menuPass has used process hollowing in iexplore.exe to load the RedLeaves implant.44
S0198 NETWIRE The NETWIRE payload has been injected into benign Microsoft executables via process hollowing.1011
S0229 Orz Some Orz versions have an embedded DLL known as MockDll that uses process hollowing and Regsvr32 to execute another payload.17
G0040 Patchwork A Patchwork payload uses process hollowing to hide the UAC bypass vulnerability exploitation inside svchost.exe.43
S0650 QakBot QakBot can use process hollowing to execute its main payload.37
S0662 RCSession RCSession can launch itself from a hollowed svchost.exe process.414042
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.25
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.1213
G0027 Threat Group-3390 A Threat Group-3390 tool can spawn svchost.exe and inject the payload into that process.4645
S0266 TrickBot TrickBot injects into the svchost.exe process.28293031
S0386 Ursnif Ursnif has used process hollowing to inject into child processes.9
S0689 WhisperGate WhisperGate has the ability to inject its fourth stage into a suspended process created by the legitimate Windows utility InstallUtil.exe.3536
S1065 Woody RAT Woody RAT can create a suspended notepad process and write shellcode to delete a file into the suspended process using NtWriteVirtualMemory.34

Mitigations

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.

Detection

ID Data Source Data Component
DS0009 Process OS API Execution

References

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