Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 9ebfce5805d0e207…

MALICIOUS

Office (OOXML) / .XLSM

21.1 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-16
MD5: 8934a43fb2419e71c1d4fd4a6de4061d SHA-1: 474160a9fcf19e51549d32f2ea283009a429d6d5 SHA-256: 9ebfce5805d0e207b38d0c8dbf627bb2864a0301b3c34ac06e5242bf29075047
250 Risk Score

Malware Insights

Emotet · confidence 95%

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

This Excel 4.0 macro-enabled document (XLSM) contains a hidden worksheet and uses dangerous formula APIs like FORMULA to download and execute a second-stage payload. The script reconstructs the string "reg&s&vr3&2.exe" which is likely intended to be saved in the "Windows\SysWow64\" directory as "rfs.dll". The document body contains multiple URLs that are likely used for this download. The ClamAV detection as Xls.Downloader.Emotet confirms the malicious nature and family.

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 http://buchhave.net/cache/t82rF5S/
    • https://www.bilandecompetences.fr/administrator/3c/
    • http://bostonseafarms.com/images/zPgXFMy8VbKNXtFp/
    • http://casazulshop.com/Adapter/yJTgSEDEpQvm/
    • http://bruiserbodies.com/images/vAj7fuqYe5y9/
    • http://brittknight.com/PHP/f/
    • http://carloshd.com/trulia/4vsUaqQd/
    • 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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