Emotet — Office (OOXML) / .XLSX malware analysis

Static analysis result for SHA-256 fd0dfb80a1cb4bbd…

MALICIOUS

Office (OOXML) / .XLSX

50.9 KB Created: 2022-03-30 21:24:25 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-31
MD5: c45986512e12b42d03c6fd5bb99de202 SHA-1: f1b4f7fd9b5661bb77d868938ab3899b71a152cd SHA-256: fd0dfb80a1cb4bbdef0cf9b9a2503563ed8679d88a305b246dce39b58a105bf7
298 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1218.010 System Binary Proxy Execution: Regsvr32 T1059.005 Command and Scripting Interpreter: Visual Basic T1105 Ingress Tool Transfer

The file is an Excel 4.0 macro-enabled spreadsheet, detected as Emotet. The macros utilize dangerous XLM functions like FORMULA to construct and execute commands. Specifically, it appears to construct a command to download and execute a DLL using regsvr32.exe from one of the embedded URLs. The reconstructed command involves downloading a DLL from http://harleyqueretaro.com/renew2019/Back2016-12-22/cv/data/RjuiFMp4Fsp/ or similar URLs and saving it as ..\rulm.dll, which is then executed via regsvr32.exe.

Heuristics 8

  • 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.Emotet04220-9942583-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet04220-9942583-0
  • 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.
  • External hyperlinks (3) low OOXML_EXTERNAL_HYPERLINKS
    Document contains 3 external hyperlinks — clickable URLs are stored as external relationships. First target: https://rumkeke.com/wp-admin/A8/","
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 7 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://harleyqueretaro.com/renew2019/Back2016-12-22/cv/data/RjuiFMp4Fsp/
    • http://hoatuoiso1.com/replace/fVea/
    • http://www.grandfurniture.com/thegrandbrands/eGd55tEm9qkPNOhViP/
    • https://rumkeke.com/wp-admin/A8/
    • https://www.restaurantgaig.com/wp-includes/HLDoANj/
    • http://www.hiway91.com/wp-content/Y/
    • 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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
2ef95bf166dbf14d5280e19f3c7c81a3e8bfde62220401b1871bb39e3fb952d3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3358 bytes

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