Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 b0775a9991c51676…

MALICIOUS

Office (OOXML) / .XLSX

84.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: d1b56e4e496f48532c77b6d31020c486 SHA-1: 547f513d39fcd032c8e08ff05bba9de05889ad93 SHA-256: b0775a9991c516761b73d2b9d9dbdf283c66c8d63c0b5af9a24abe70cf912346
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1218.011 System Binary Proxy Execution: Rundll32 T1059.001 Command and Scripting Interpreter: PowerShell T1105 Ingress Tool Transfer

This XLSX file contains Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET and OOXML_XLM_DANGEROUS_FN heuristics. The macros leverage dangerous functions like FORMULA to call Win32 APIs, specifically using rundll32.exe to download a payload from one of the embedded URLs. The ClamAV detection as 'Xls.Downloader.EmotetExcel01223-9936530-0' strongly suggests the Emotet family. The reconstructed command line 'rundll32.exe D"&"l"&"lR"&"egister"&"Serve"&"r \Windows\urlmon' and the target URL 'http://online.libertyinvestmentbank.com/__MACOSX/2LbJ1s8tojqtw0/' are key indicators of this downloader behavior.

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 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.EmotetExcel01223-9936530-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.EmotetExcel01223-9936530-0
  • 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 3 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://online.libertyinvestmentbank.com/__MACOSX/2LbJ1s8tojqtw0/
    • http://vlogingcamerareview.xyz/wp-includes/nveHidp/
    • http://dpmcompras.xyz/wp-content/R28snV2ko7tgD7yuIVa/
    • 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
6fb9d96d745e6a97b95958af3e421aea342153dc862581839ac836f7728985da		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 2794 bytes

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