Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 bffbeb92e1f3eb44…

MALICIOUS

Office (OOXML) / .XLSX

100.0 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: e4f616a8700ff79b3965fe95020da11e SHA-1: 81d7cdf07fb775bab8455e8649e7370d29e390a3 SHA-256: bffbeb92e1f3eb445f08b0424aca835259eaab7f77a3137dba02c94edfc7b50a
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1218.011 Signed Binary Proxy Execution: Rundll32 T1105 Ingress Tool Transfer

The sample is an Excel file containing Excel 4.0 macros, identified by the OOXML_XLM_MACROSHEET heuristic. The macros utilize dangerous functions like FORMULA to download a payload from multiple URLs, including "https://bossblogg.com/wp-includes/sOfCzg6/". The SE_LOLBIN_RUN_COMMAND heuristic indicates the use of rundll32.exe to execute the downloaded payload from "iix.ocx". The ClamAV detection as "Xls.Downloader.EmotetExcel01222-9935624-0" strongly suggests the Emotet family.

Heuristics 7

  • 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, RETURN 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
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • 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://bossblogg.com/wp-includes/sOfCzg6/
    • http://blog.easy-firmware.com/wp-admin/HL7v6fuya4C6Zpy/
    • https://theisdr.org/webinar/JbOrwW4JHlQP/
    • https://globalhomepackers.com/wp-content/r/
    • https://vippark.biz/dr2j9p/hzNQ7/
    • 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
d810cc87eb589e5f09a9a5cb06e9b818ff37e1b4d0032ba08fbf4b3620a5d223		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3431 bytes

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