Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 41821381e38770d4…

MALICIOUS

Office (OOXML) / .XLSX

83.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: e2ca5460365effba7e08b586cd468730 SHA-1: 5f14eeccf40de660b5caf67b3f3f39e4a4ed2724 SHA-256: 41821381e38770d4b4eb06654fec731e89e45185dec97fac4dbef59560bb3fa9
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1204.002 Malicious Link: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell T1105 Ingress Tool Transfer

This Excel 4.0 macro-enabled document utilizes dangerous functions like FORMULA to call Win32 APIs. The embedded URL `https://kauffmancreates.com/images/G8050LVq/` is used in conjunction with `rundll32.exe` to download and execute a second-stage payload. The ClamAV signature 'Xls.Downloader.EmotetExcel01223-9936530-0' strongly suggests the Emotet family. The macro also attempts to construct a command using `rundll32.exe D"&"l"&"lR"&"egister"&"Serve"&"r \Windows\urlmon` and `rundll32.exe D"&"l"&"lR"&"egister"&"Serve"&"r SysWow64\` to facilitate the download.

Heuristics 7

  • Excel 4.0 macro sheet (1 sheet(s)) critical OOXML_XLM_MACROSHEET
    Spreadsheet contains an Excel 4.0 (XLM) macro sheet — XLM was a major Office malware vector during 2020-2022 and evaded many VBA-focused controls before Microsoft tightened XLM defaults. Even legitimate XLM use is rare in modern workbooks.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: FORMULA critical OOXML_XLM_DANGEROUS_FN
    Excel 4.0 macro sheet uses formula APIs that call directly into Win32 (=CALL/=EXEC/=REGISTER/=FORMULA). These are the primitives used to download payloads, write files, and start processes from an XLM macro without invoking VBA.
  • ClamAV: Xls.Downloader.EmotetExcel01223-9936530-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel01223-9936530-0
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 3 hidden sheet(s) — hidden sheets are commonly used to conceal macro code, staging data, or intermediate payload construction
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL https://kauffmancreates.com/images/G8050LVq/
    • https://sanagrafix.com/udll/fki4w1vFApT4Rwjp1R/
    • http://unifiedpharma.com/wp-admin/ildi5K2aTIrdvEobQ/
    • http://schemas.openxmlformats.org/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
6fb9d96d745e6a97b95958af3e421aea342153dc862581839ac836f7728985da		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 2794 bytes

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