Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 437c9dc0bdd6d3b5…

MALICIOUS

Office (OOXML) / .XLSX

99.2 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: fde31fd80f4506b7d5a10966f39513c7 SHA-1: b4da2ada37a88dc06a98f838579b0c3601295f59 SHA-256: 437c9dc0bdd6d3b561122500de59d0cdbbb55232d97eaee3fd6b7cbcebb1743a
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1071.001 Web Protocols

This Excel 4.0 macro sheet utilizes dangerous functions like FORMULA to call Win32 APIs. The script attempts to download a file named 'iix.ocx' from the URL 'https://grandeestudio.com/suqnugjm/msPWLXZBJiTYtyOGXx/' using rundll32.exe and then execute it. This is a common delivery mechanism for Emotet, which often uses macro-enabled documents to download and install its payload.

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, 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
  • 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://grandeestudio.com/suqnugjm/msPWLXZBJiTYtyOGXx/
    • 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
928f85ed00cbeb9bc82579750322f8cb22033ec793f84667d905d7c8fcb8cbc6		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3477 bytes

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