Detect Extra Window Memory Injection in Sumo Logic CSE
Adversaries may inject malicious code into process via Extra Window Memory (EWM) in order to evade process-based defenses as well as possibly elevate privileges. EWM injection is a method of executing arbitrary code in the address space of a separate live process. Before creating a window, graphical Windows-based processes must prescribe to or register a windows class, which stipulate appearance and behavior via windows procedures. Registration of new windows classes can include a request for up to 40 bytes of EWM. Although small, the EWM is large enough to store a 32-bit pointer and is often used to point to a windows procedure. Malware may utilize this memory location in part of an attack chain that includes writing code to shared sections of the process's memory, placing a pointer to the code in EWM, then invoking execution by returning execution control to the address in the process's EWM.
MITRE ATT&CK
- Technique
- T1055 Process Injection
- Sub-technique
- T1055.011 Extra Window Memory Injection
- Canonical reference
- https://attack.mitre.org/techniques/T1055/011/
Sumo Detection Query
_sourceCategory="windows/sysmon" EventCode=10
| where TargetImage matches "*\\explorer.exe"
| where GrantedAccess in ("0x1FFFFF", "0x001F0FFF", "0x1F3FFF", "0x0020", "0x1F1FFF")
| where !(SourceImage matches "*\\explorer.exe" or SourceImage matches "*\\csrss.exe" or SourceImage matches "*\\dwm.exe" or SourceImage matches "*\\winlogon.exe" or SourceImage matches "*\\ShellExperienceHost.exe" or SourceImage matches "*\\SearchUI.exe" or SourceImage matches "*\\taskhostw.exe" or SourceImage matches "*\\sihost.exe")
| parse regex field=SourceImage "\\\\(?P<InjectorName>[^\\\\]+)$"
| if (GrantedAccess == "0x1FFFFF", "Critical - PROCESS_ALL_ACCESS",
if (GrantedAccess == "0x001F0FFF", "High - Full process rights",
if (GrantedAccess == "0x0020", "Medium - PROCESS_VM_WRITE",
"Medium - Suspicious access rights"))) as EWMSeverity
| fields _messageTime, Computer, User, SourceImage, InjectorName, TargetImage, GrantedAccess, EWMSeverity
| sort by _messageTime descSumo Logic query detecting EWM injection by parsing Sysmon EventCode 10 process access events targeting explorer.exe, filtering to suspicious access masks and excluding known legitimate Windows system processes, with severity enrichment based on granted access level.
Data Sources
Required Tables
False Positives & Tuning
- Enterprise endpoint security platforms with active protection modules that inject monitoring threads into explorer.exe and require PROCESS_ALL_ACCESS or equivalent rights
- IT automation and software distribution platforms (SCCM, Intune management extension, BigFix) that access explorer.exe during policy application or user environment configuration
- Legitimate application compatibility shims or third-party shell extension DLLs that access explorer.exe memory during initialization of explorer-hosted components
Other platforms for T1055.011
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 1Enumerate Shell_TrayWnd Window Handle
Expected signal: Sysmon Event ID 1: PowerShell execution with FindWindowW in command line. API call to FindWindowW with class name Shell_TrayWnd logged by ETW if user32.dll API tracing is enabled.
- Test 2GetWindowLong Extra Memory Read
Expected signal: Sysmon Event ID 1: PowerShell execution with GetWindowLongPtrW. ETW: user32.dll API calls for FindWindowW and GetWindowLongPtrW.
- Test 3Cross-Process Memory Write to Explorer
Expected signal: Sysmon Event ID 1: PowerShell execution. If actual OpenProcess with write rights is called: Sysmon Event ID 10 (ProcessAccess) from PowerShell to explorer.exe with PROCESS_VM_WRITE.
References (5)
- https://attack.mitre.org/techniques/T1055/011/
- https://www.malwaretech.com/2013/08/powerloader-injection-something-truly.html
- https://www.welivesecurity.com/2013/03/19/gapz-and-redyms-droppers-based-on-power-loader-code/
- https://www.endgame.com/blog/technical-blog/ten-process-injection-techniques-technical-survey-common-and-trending-process
- https://msdn.microsoft.com/library/windows/desktop/ms633591.aspx
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