Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 345075974a633202…

MALICIOUS

Office (OOXML) / .XLSX

49.5 KB Created: 2022-01-20 15:33:32 UTC Authoring application: Microsoft Excel 16.0300
MD5: 091c24760470154fc629ef6287b439ad SHA-1: bc21f082f63688d18667424e60fef6d7f261b65b SHA-256: 345075974a633202c20da7f744cce921ae20061720ea5d27a474adcc15258a56
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution T1105 Ingress Tool Transfer

The file contains critical heuristic firings indicating Excel 4.0 macros, including the use of dangerous functions like EXEC and HALT. The macro code reconstructs a command to execute 'mshta' with a URL, indicating it's designed to download and execute a second-stage payload. ClamAV detection further confirms this as an Emotet downloader variant.

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: EXEC, HALT 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.EmotetExcel02221-9938900-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel02221-9938900-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 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://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
2628f526ad89b679a894d8f4330dd515993bf15dcb910d61c44994f9a088c9d8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1601 bytes

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