Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 3965d387bca2c8ee…

MALICIOUS

Office (OOXML) / .XLSX

100.0 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 7d03d19d00fc06210a9037d95f824ff2 SHA-1: 66e0e47541ba352cea4b86d51a7f61e358d3606e SHA-256: 3965d387bca2c8ee4cfdb7e384ecc5578658988d2d5baea357ec1ca97693c677
290 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample is an Excel file containing Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous formula APIs like FORMULA to download and execute payloads. Specifically, the script constructs a command to execute 'rundll32.exe' with arguments pointing to a malicious DLL and a URL from which to download it. The reconstructed URL is "https://burialinsurancelab.com/q5kje9/K1mF/". This behavior is consistent with Emotet's typical delivery mechanism.

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, RETURN 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.EmotetExcel01222-9935624-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel01222-9935624-0
  • 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 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://burialinsurancelab.com/q5kje9/K1mF/
    • https://edgetactical.ritabilisim.com/admin/2jKBEGDY0XpcgxF7f/
    • https://lealracecars.com/donnacox/fVqOYBzAUoU/
    • https://4seasonsflorals.com/yhedjkl/BYwyXorqDywx/
    • https://boldconsulting.info/bkzh6v/eqbAgc3oMGBsC5VDn1w/
    • 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
d810cc87eb589e5f09a9a5cb06e9b818ff37e1b4d0032ba08fbf4b3620a5d223		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3431 bytes

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