Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 3c8b54def22442aa…

MALICIOUS

Office (OOXML) / .XLSX

83.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 1e8632ebd6add0a60c782d9aac850f47 SHA-1: b178c2234f6f0b5b3829698953623f62965ef812 SHA-256: 3c8b54def22442aaa334cbae48263d897ca2d62d76dc4df4e6efb03849d8c2a7
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1218.011 System Binary Proxy Execution: Rundll32 T1105 Ingress Tool Transfer

The sample is an Excel 4.0 macro-enabled spreadsheet. Critical heuristics indicate the use of dangerous XLM formula APIs like FORMULA, which are known to be used for downloading and executing payloads. The embedded URLs and the explicit use of 'rundll32.exe' in the document body strongly suggest that the macro's intent is to download and execute a second-stage payload from one of the provided URLs. The ClamAV detection name 'Xls.Downloader.EmotetExcel01223-9936530-0' further supports the Emotet family attribution.

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 http://15.237.135.38/dza9hr/kjt6/
    • http://wateringcanreview.xyz/wp-includes/css/qky11a/
    • http://cakemixturereview.xyz/wp-includes/U2ayYVCPRhWqERyw4/
    • 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
94ce481067ff50aad11a63e7c0d34887a339fe2ee9932e266cd1503beaa545b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3034 bytes

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