Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 37dd9f3bae82ac2c…

MALICIOUS

Office (OOXML) / .XLSX

84.3 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 1ff3fe984b43bce38bc5f714cb864b9d SHA-1: 4141b5c02a28eda6d43640cb1b5f9b2f7672717d SHA-256: 37dd9f3bae82ac2c5d9ba22974194058fbe9d9de23941450763c481f2a2a95d2
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 sample utilizes Excel 4.0 macros, a known technique for delivering Emotet. The macro contains a formula that calls `rundll32.exe` to download and execute a payload from one of the provided URLs. Specifically, the macro constructs a command that includes the URL `http://online.libertyinvestmentbank.com/__MACOSX/2LbJ1s8tojqtw0/` and attempts to save it as `.. i.ocx`. The use of dangerous XLM formula APIs like `FORMULA` to directly invoke Win32 functions is a critical indicator of malicious intent.

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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