Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 3a3bb73db9bf3049…

MALICIOUS

Office (OOXML) / .XLSX

68.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 4bc01f92d39e27892622f9bc976fe802 SHA-1: 50ce682935f34a76736d375595fbb341aeaba674 SHA-256: 3a3bb73db9bf30495a2c40cb6d31fc8684bdd481c9aaa57fcdc47baeace7021b
290 Risk Score

Malware Insights

Emotet · confidence 95%

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

The sample contains Excel 4.0 macros that leverage dangerous API functions like FORMULA to construct and execute commands. Specifically, it uses rundll32.exe to load 'iix.ocx' from the SysWow64 directory, which is then instructed to download a payload from one of the provided URLs. The ClamAV detection and the presence of multiple malicious URLs strongly indicate the Emotet family, known for its downloader capabilities.

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.EmotetExcel02221-9938627-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel02221-9938627-0
  • 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 http://revueagricole.com/wp-admin/iJDi9Hbqe/
    • http://galabet.blog/2np65ok/IZgE/
    • https://sudaneseacademy.com/wp-admin/VjXNzK7L0uuJsdM9PKi/
    • https://didorenko.org/review/cAAweb70J2VO/
    • https://frankiesfamily.org/cgi-bin/jc3CSTWMVQDE9J7h6/
    • 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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