Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 1c5b9be744e31213…

MALICIOUS

Office (OOXML) / .XLSM

48.9 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-15
MD5: 852e53cce21c9356e3ab56072c651821 SHA-1: f5c78276da8123bb860c0f745ea25c675a548138 SHA-256: 1c5b9be744e31213b6defc3c40976fca0afc36a61200ef3aa5b28f6476e8fbf6
290 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Visual Basic T1218.010 System Binary Proxy Execution: Regsvr32 T1059.001 PowerShell T1105 Ingress Tool Transfer

This XLSM file contains Excel 4.0 macros, including an Auto_Open macro, which is a critical indicator of malicious intent. The macros utilize dangerous functions like FORMULA to construct and execute commands. Specifically, it appears to be downloading a payload from one of the provided URLs using regsvr32.exe, as evidenced by the heuristic firing SE_LOLBIN_RUN_COMMAND and the reconstructed command line in the DOC BODY. The ClamAV detection as 'Xls.Downloader.Emotet03222-9941793-0' strongly suggests the Emotet family.

Heuristics 7

  • Excel 4.0 macro sheet (3 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.Emotet03222-9941793-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03222-9941793-0
  • 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 6 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://www.arkpp.com/ARIS-BSU/9K1/
    • http://www.babylinesl.com/catalog/iVsl6YvlyIyX/
    • https://unada.us/acme-challenge/3NXwcYNCa/
    • https://alebit.de/css/gqKtdKmTsC4iDh/
    • http://www.avrworks.com/mail/0Z4GbaKuDTGprJ/
    • https://physioacademy.co.uk/blog/Qs8QZTp0Z6nKf9YjVBMS/
    • https://automobile-facile.fr/wp-admin/QV/
    • 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
137a925c2f887993c01c62d855214355cff109c22db9290f097ecabd120f99d4		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3854 bytes
xlm_sheet_01.xml
2a32255d366aec230ab40f23366f68866138e6b74b9e90667eb0b4bfdffdeb22		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1276 bytes
xlm_sheet_02.xml
d04ed330dbcc9611b697c4bc3f00d6bfe568e76c8e476bc4dd6395076f22ee74		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1213 bytes

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