Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 91c20c86528c2e48…

MALICIOUS

Office (OOXML) / .XLSX

103.0 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 1f4d700f0131ec27bfefd41b61024632 SHA-1: 87a191da1254c5cdf3ec7034d89a27174ad89efb SHA-256: 91c20c86528c2e48b8378a697073fb4dd87f8d682dd964a215baa6d2124a78a7
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Service Execution T1059.001 PowerShell: PowerShell T1218.011 Signed Binary Proxy Execution: Rundll32 T1105 Ingress Tool Transfer

This Excel 4.0 macro-enabled document contains critical heuristics indicating the use of dangerous functions like FORMULA, which can call Win32 APIs. The DOC BODY reveals that the macro attempts to download a file using 'rundll32.exe' and 'urlmon.dll's DownloadToFile function from multiple URLs. The ClamAV detection as 'Xls.Downloader.EmotetRed02223-9938636-0' strongly suggests the Emotet family. The reconstructed URLs are: "http://landorestates.com/wordpress/wordpress/NELf96wr/", "http://butzigerr.com/meeting/hBJCeNGAvBpGZoD7ee/", "https://www.rockwoodsaloon.com/wp-admin/A706GTXNufQSWXG52/", "https://teamsanddeep.com/wp-content/p3f2n6wcnwfg/", and "https://csinoticias.com/wp-includes/RnHjIzg/".

Heuristics 6

  • Excel 4.0 macro sheet (3 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.EmotetRed02223-9938636-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetRed02223-9938636-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 6 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

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
5a62a357cb895c98dc30b4c4c5c056eac8ac1b92bc088a5bcf20517cbcd838f8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3434 bytes
xlm_sheet_01.xml
c70a51acb5791492ef3f1e96d2217abba4360bc0964fdbbf0b281da430450073		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 908 bytes
xlm_sheet_02.xml
84b5606b26315521210c94dce2556ab11c1d4148efb57521cf114d2065ef725b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 905 bytes

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