Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 9a8a7fda56e4863c…

MALICIOUS

Office (OOXML) / .XLSM

21.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-17
MD5: 4337f755ce0e4e174853e2b9e26c0164 SHA-1: 3e785993b27c0dfbb1e025bf7eadb3d392f11223 SHA-256: 9a8a7fda56e4863c4ed9cc9340cc413005de3a619b1c9c790b007348597da0e4
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1071.001 Web Protocols

The file is an XLSM document containing Excel 4.0 macros, identified by the 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_AUTOOPEN_DEFINEDNAME' heuristics. The macros utilize dangerous XLM functions like FORMULA to download and execute payloads from a list of URLs, as indicated by the 'OOXML_XLM_DANGEROUS_FN' firing and the embedded URLs. The ClamAV detection and the nature of the macros strongly suggest it belongs to the Emotet family, which commonly uses this delivery method. The script reconstructs the command 'regsvr32.exe rfs.dll' which is used to execute the downloaded payload.

Heuristics 6

  • 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.Emotet03220-9941789-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03220-9941789-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 4 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://www.almoeqatar.com/cgi-bin/3g/
    • http://www.lavameapp.com.ar/slide-images/7bzQevDGMld/
    • http://cenaf.com.co/error/TpewL/
    • http://baykusoglu.com.tr/wp-admin/317Sz3wZsYmAAmmL6/
    • http://www.ayelet.info/wp-admin/oHRoG0X9ubuNtQ/
    • http://lista33rivera.uy/wp-content/jiBtjSaJMcM/
    • http://pusatbahasa.unsyiah.ac.id/backup/qWzXJpGddclh4zZjt/
    • 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
f9ef0dd03a642623a126a648a3e3b498d8403d13558799b8b55ca81a239f78e5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3968 bytes

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