Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 24466c9b7124aec9…

MALICIOUS

Office (OOXML) / .XLSX

115.8 KB Created: 2022-01-19 18:30:24 UTC Authoring application: Microsoft Excel 16.0300
MD5: 63cd212e4af652355f895618a21e17ca SHA-1: 821ca967c57362b26381f61395d1ff3d3fdc98fb SHA-256: 24466c9b7124aec9a583ebd09b6df592c6a2eba41701a9f78a6ed1142e708614
258 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 PowerShell T1204.002 Malicious Link T1059.001 PowerShell T1059.003 Windows Command Shell T1105 Ingress Tool Transfer

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by multiple critical heuristic firings including 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_DANGEROUS_FN'. The macros utilize the 'EXEC' function to run a command that downloads a second-stage payload from the reconstructed URL 'http://0x5cff39c3/sec/se1.html'. The 'SE_INVOICE_LURE' heuristic further suggests the document body is intended to trick the user into interacting with the malicious content. The ClamAV detection also confirms this is a known Emotet variant.

Heuristics 7

  • 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: EXEC, HALT 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.EmotetExcel01220-9936739-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel01220-9936739-0
  • 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
  • Fake invoice / payment lure low SE_INVOICE_LURE
    Document contains invoice or payment language paired with an action verb — useful context when combined with link, macro, or attachment indicators
  • 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
c1622bb80274cc8ed04d23560af8010a40daa043900958e290e422b4ea97bce3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1793 bytes
xlm_sheet_01.xml
34df557a4264643e04826099857eec235e89f2ca36dac5385be0c73ed1b1dfe5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1086 bytes
xlm_sheet_02.xml
c1a67afdf06fee625909f1fea6d48d49f9c71a5bcf019cff1d07cdb3f0a81aa1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.xml 1086 bytes

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