Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 3e8109803e78bd1d…

MALICIOUS

Office (OOXML) / .XLSM

101.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 9198d0316a80cc467a191cb1053ade81 SHA-1: a4c4763d8fa6770c4107bcad41718fdbf821bc09 SHA-256: 3e8109803e78bd1d83e880576f4bc16bd2f25c6591dd708d8c00aa9b3cd90f74
250 Risk Score

Malware Insights

Emotet · confidence 95%

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

The file is an XLSM document 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 FORMULA API to construct and execute commands. Specifically, it reconstructs the string 'URLDownloadToFile' and uses it to download a file from one of the provided URLs, such as 'http://mgah.flywheelsites.com/images/zP9T0F2pW4wwv/', into 'bestb.ocx'. It then attempts to execute this downloaded file using 'rundll32.exe'. The ClamAV detection also explicitly names this as an Emotet variant.

Heuristics 6

  • Excel 4.0 macro sheet (7 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.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 9 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 7

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
f338eca76c2e0738c608a2450e1cc09c08507adc28bcb4242847ee61fa91cd19		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3051 bytes
xlm_sheet_01.xml
c03621be3a225428d2db00c9421c64f413ea46043a63bf8b5410938a779a082a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1277 bytes
xlm_sheet_02.xml
5248676e3f66fb2b5c3ae6588b7110316409b0edb33e54ef910732f74ba69037		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1274 bytes
xlm_sheet_03.xml
a0c0a2dcc388c957c54d01786976582823e6fe5d8bd7735126a05265eb7642ac		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.xml 1274 bytes
xlm_sheet_04.xml
bb4f0217ff170e4684568f8ac51861b68f14a34de7d8de660c1a91abdfe369e7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet4.xml 1277 bytes
xlm_sheet_05.xml
aef646c5e05896b5cdffa18b5334064062057a419c62277983f702f16c4cf563		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet5.xml 1274 bytes
xlm_sheet_06.xml
0f99e368277b58b95b4aae6ff0f2fb8230df060b275dce46a578c6b8a735f1f3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet6.xml 1274 bytes

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