Detect Embedded Payloads in CrowdStrike LogScale
Adversaries may embed payloads within other files to conceal malicious content from defenses. Otherwise seemingly benign files (such as scripts and executables) may be abused to carry and obfuscate malicious payloads and content. Adversaries have been observed embedding payloads as PE overlays, within resource sections of legitimate binaries, inside LNK file ExtraData fields, within Office VBA macros, and nested inside other file types. Notable examples include Emotet embedding executables in dropper binaries, DEADEYE embedding payloads in compiled binaries, Lazarus Group distributing malicious payloads in PNG files, Pikabot loading encrypted chunked PE sections, and Uroburos storing executable payloads in encrypted Queue files.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1027 Obfuscated Files or Information
- Sub-technique
- T1027.009 Embedded Payloads
- Canonical reference
- https://attack.mitre.org/techniques/T1027/009/
LogScale Detection Query
#event_simpleName = /^(ProcessRollup2|SyntheticProcessRollup2|FileWritten)$/
| case {
#event_simpleName = /ProcessRollup2/
| FileName = /(?i)certutil\.exe$/
| CommandLine = /(?i)-(decode|urlcache)/
| CommandLine = /(?i)\.(exe|dll|bin|dat|cfg)/
| DetectionType := "CertutilDecode" ;
#event_simpleName = /ProcessRollup2/
| FileName = /(?i)(expand|extrac32|makecab)\.exe$/
| CommandLine = /(?i)\.(exe|dll|bin)/
| DetectionType := "ExpandExtract" ;
#event_simpleName = /FileWritten/
| TargetFileName = /(?i)\.(exe|dll|bin|shellcode)$/
| ImageFileName = /(?i)(WINWORD|EXCEL|POWERPNT|AcroRd32|FoxitPDFReader|wscript|cscript|mshta)\.exe$/
| DetectionType := "OfficeBinaryDrop"
}
| table(
[_time, ComputerName, UserName, FileName, CommandLine,
ImageFileName, TargetFileName, DetectionType]
)
| sort(field=_time, order=desc)CrowdStrike LogScale (Falcon) query detecting T1027.009 Embedded Payloads across three branches using a case expression over ProcessRollup2 and FileWritten sensor events: CertutilDecode identifies certutil -decode/-urlcache against binary formats; ExpandExtract flags expand/extrac32/makecab dropping executables; OfficeBinaryDrop detects FileWritten events for executables created by Office, Acrobat, or Windows script host processes. Events not matching any branch are dropped.
Data Sources
Required Tables
False Positives & Tuning
- Falcon-monitored endpoints where IT automation invokes certutil.exe for legitimate certificate management operations such as importing root CA certificates or generating PKCS#7 encoded trust bundles with .bin output paths
- Enterprise software packaging workflows that use makecab.exe or expand.exe as part of MSI bootstrapper or ClickOnce deployment routines, triggering the ExpandExtract branch during sanctioned application rollouts
- Microsoft Office add-ins or third-party COM objects that write new .dll components to the user profile or program files during plugin update cycles, generating OfficeBinaryDrop telemetry from WINWORD.EXE or EXCEL.EXE
Other platforms for T1027.009
Testing Methodology
Validate this detection against 4 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 1Extract Embedded Payload from PE Overlay with certutil
Expected signal: Sysmon Event ID 1: certutil.exe with -encode and then -decode arguments. Sysmon Event ID 11: encoded_payload.txt and extracted_payload.exe created in %TEMP%. The -decode operation creates an executable from a text file.
- Test 2Office Macro Dropping Embedded Executable
Expected signal: Sysmon Event ID 1: PowerShell spawning Word COM object. Word process creating a document with VBA code. File creation of macro_test.doc.
- Test 3Embed Payload in PE Resources Section
Expected signal: PowerShell process creation demonstrating the concept. Binary data file creation in %TEMP%.
- Test 4Extract Payload from LNK ExtraData Field
Expected signal: Sysmon Event ID 11: embedded_lnk.lnk created in %TEMP%. Sysmon Event ID 1: cmd.exe spawned from LNK execution with arguments. Sysmon Event ID 11: lnk_output.txt created.
References (5)
- https://attack.mitre.org/techniques/T1027/009/
- https://github.com/peewpw/Invoke-PSImage
- https://www.cisa.gov/uscert/ncas/analysis-reports/ar20-303a
- https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-shllink/c41e062d-f764-4f13-bd4f-ea812ab9a4d1
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1027.009/T1027.009.md
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