Detect Dynamic-link Library Injection in Splunk
Adversaries may inject dynamic-link libraries (DLLs) into processes in order to evade process-based defenses as well as possibly elevate privileges. DLL injection is commonly performed by writing the path to a DLL in the virtual address space of the target process before loading the DLL by invoking a new thread. The write can be performed with native Windows API calls such as VirtualAllocEx and WriteProcessMemory, then invoked with CreateRemoteThread (which calls the LoadLibrary API responsible for loading the DLL). Variations include reflective DLL injection (self-mapping DLL), memory module loading, and Module Stomping/DLL Hollowing where a legitimate DLL is loaded then its AddressOfEntryPoint is overwritten before execution.
MITRE ATT&CK
- Technique
- T1055 Process Injection
- Sub-technique
- T1055.001 Dynamic-link Library Injection
- Canonical reference
- https://attack.mitre.org/techniques/T1055/001/
SPL Detection Query
index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=8
| rename SourceImage as InjectorProcess, TargetImage as TargetProcess
| eval InjectorName=mvindex(split(InjectorProcess, "\\"), -1)
| eval TargetName=mvindex(split(TargetProcess, "\\"), -1)
| search NOT InjectorProcess IN ("*\\MsMpEng.exe", "*\\csrss.exe", "*\\services.exe", "*\\lsass.exe")
| join type=left TargetProcessId=TargetProcessId host [search index=wineventlog sourcetype="XmlWinEventLog:Microsoft-Windows-Sysmon/Operational" EventCode=7 NOT (ImageLoaded="C:\\Windows\\System32\\*" OR ImageLoaded="C:\\Windows\\SysWOW64\\*" OR ImageLoaded="C:\\Program Files*")
| rename ProcessId as TargetProcessId, ImageLoaded as InjectedDLL
| fields _time, host, TargetProcessId, InjectedDLL]
| where isnotnull(InjectedDLL)
| table _time, host, User, InjectorProcess, TargetProcess, StartModule, StartFunction, InjectedDLL
| sort - _timeDetects DLL injection by correlating Sysmon Event ID 8 (CreateRemoteThread) with Event ID 7 (ImageLoad) for DLLs loaded from non-standard paths in the target process. The join links the thread creation to the DLL load in the target, providing both the injection source and the injected DLL path for analysis.
Data Sources
Required Sourcetypes
False Positives & Tuning
- EDR and antivirus products performing legitimate DLL injection for process monitoring
- Application compatibility shims loading DLLs via apphelp.dll
- APM/instrumentation tools injecting agent DLLs into monitored applications
- Browser extensions loading plugin DLLs
Other platforms for T1055.001
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1DLL Injection via mavinject.exe (LOLBAS)
Expected signal: Sysmon Event ID 1: Process Create for mavinject.exe with CommandLine containing /INJECTRUNNING. Sysmon Event ID 8: CreateRemoteThread from mavinject.exe targeting notepad.exe. Sysmon Event ID 7: ImageLoad of amsi.dll in notepad.exe process.
- Test 2Reflective DLL Injection via PowerSploit Invoke-DllInjection
Expected signal: Sysmon Event ID 1: PowerShell process creation. Sysmon Event ID 3: Network connection to raw.githubusercontent.com. Sysmon Event ID 8: CreateRemoteThread from PowerShell to notepad.exe. PowerShell ScriptBlock Log Event ID 4104 with Invoke-DllInjection content.
- Test 3CreateRemoteThread DLL Injection via C# Executable
Expected signal: Sysmon Event ID 1: Process Create for csc.exe (C# compiler) spawned by PowerShell. Sysmon Event ID 1: injector_test.exe execution. Sysmon Event ID 11: File Create for injector_test.exe in TEMP. If full injection is performed: Sysmon Event ID 8 for CreateRemoteThread.
References (7)
- https://attack.mitre.org/techniques/T1055/001/
- https://www.endgame.com/blog/technical-blog/ten-process-injection-techniques-technical-survey-common-and-trending-process
- https://www.endgame.com/blog/technical-blog/hunting-memory
- https://blog.f-secure.com/hiding-malicious-code-with-module-stomping/
- https://www.ired.team/offensive-security/code-injection-process-injection/modulestomping-dll-hollowing-shellcode-injection
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1055.001/T1055.001.md
- https://lolbas-project.github.io/lolbas/Binaries/Mavinject/
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