Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 0ca9f1b39049d0a0…

MALICIOUS

Office (OOXML) / .XLSM

73.5 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-15
MD5: 952484269c7a567ab315067866490caa SHA-1: 28c976c30bf3e3956ac80b959d28461d62a26442 SHA-256: 0ca9f1b39049d0a028bc1e56c4a791f0f72e36666cd5200c0b45b484fc326fb1
250 Risk Score

Malware Insights

Emotet · confidence 95%

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

This Excel 4.0 macro-enabled document (XLSM) contains critical heuristics indicating the use of dangerous Excel 4.0 macro functions like FORMULA, which are known to be used for downloading and executing payloads. The reconstructed URL 'http://onlytesting.uknowva.com/cgi-bin/ykwkwDElL7GqV/' is used to download a second-stage payload, and the macro also attempts to write 'regsvr32.exe' to the SysWow64 directory. The ClamAV detection as 'Xls.Downloader.Emotet03220-9941786-0' strongly suggests an Emotet family infection.

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.Emotet03220-9941786-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03220-9941786-0
  • 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
    • 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
137a925c2f887993c01c62d855214355cff109c22db9290f097ecabd120f99d4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3854 bytes
xlm_sheet_01.xml
2a32255d366aec230ab40f23366f68866138e6b74b9e90667eb0b4bfdffdeb22		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1276 bytes
xlm_sheet_02.xml
7105c38c978cda99f6296f5a3515ce8f5b4eddc47e50405777a7b252f1ba8dcf		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1201 bytes

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