Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 c80c966715aecbd2…

MALICIOUS

Office (OOXML) / .XLSX

83.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 427368398d76f2f7086a5624e2ea1f16 SHA-1: 80c3526bda273036f9944e5d11144164c8668567 SHA-256: c80c966715aecbd2b43dc364131511eb0db0ce5046eebe576750f2132e0be6c9
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

The sample is an Excel 4.0 macro-enabled spreadsheet. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like FORMULA, CALL, EXEC, and REGISTER, which are commonly used to download and execute payloads. The 'SE_LOLBIN_RUN_COMMAND' heuristic and the reconstructed DOC BODY content reveal the use of 'rundll32.exe' with 'urlmon.dll' to download a file from multiple URLs, specifically 'http://kopbhawan.com/mdphht/fwqEBVQlJXHayt/', 'http://adi.iswks.com/assets/hO1v71pqfNN/', and 'http://towardsun.net/admin/dcg3jSLkPuYsQ5xB/', and save it as '..\wxeu.ocx'. This functionality aligns with the ClamAV detection of 'Xls.Downloader.EmotetExcel01223-9936530-0', strongly suggesting Emotet family activity.

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 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.EmotetExcel01223-9936530-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel01223-9936530-0
  • 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 3 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://kopbhawan.com/mdphht/fwqEBVQlJXHayt/
    • http://adi.iswks.com/assets/hO1v71pqfNN/
    • http://towardsun.net/admin/dcg3jSLkPuYsQ5xB/
    • http://kopbhawan.com/mdph
    • 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
bc434a02f8174c59a684fc724af55a55ed12e02f1e0886ee1818bcfaa8302510		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 2827 bytes

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