Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 b5cd9e2390685a01…

MALICIOUS

Office (OOXML) / .XLSM

20.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-17
MD5: a1be5abe895142ef9ba1e598e7788a76 SHA-1: cdb088fd03f0e56fb27a715be69b7058a2484511 SHA-256: b5cd9e2390685a01d746a3c8e248beac5c5ff093b703019dc876eb58e8713dad
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1059.001 PowerShell T1204.002 Malicious File T1071.001 Web Protocols T1059.003 Windows Command Shell

This XLSM file contains Excel 4.0 macros, specifically utilizing the FORMULA API, which is a known technique for downloading and executing payloads. The macros reconstruct URLs and commands to download a second-stage payload, likely a PE file, and execute it using regsvr32. The ClamAV signature also confirms this as an Emotet downloader. The reconstructed URL 'https://canismallorca.es/wp-admin/OTyeYrx9C9BvYvVb3/' and the reconstructed command 'regsvr32.exe C:\windows\SysWow64\kytk.dll' are key indicators of this malicious activity.

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 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.Emotet03220-9941789-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03220-9941789-0
  • 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://canismallorca.es/wp-admin/OTyeYrx9C9BvYvVb3/
    • http://www.cafe-kwebbel.nl/layouts/3Wkev/
    • http://borbajardinagem.com.br/erros/vlB3f6XpsZG/
    • http://belleile-do.fr/diapo-ile/EeBHyfGoKYACY/
    • http://capslock.co.za/wp-includes/LMngUUTuanBofr5zK/
    • http://bkps.ac.th/b91-std63/Ixv52m8gu4aaUiyb/
    • http://www.best-design.gr/_errorpages/9wCa7GLI0cl6nM/
    • 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
bd1141b96e73c592d43d300feb4a2bed92034dffba7d5e49bf95a81f1348fbbc		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 4144 bytes

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