Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 31c2ceba5327e311…

MALICIOUS

Office (OOXML) / .XLSM

21.0 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-18
MD5: f49c7ab123a7df888787cb0b73d02d05 SHA-1: 8804266fe71a9504865ecd51d93305869ce07505 SHA-256: 31c2ceba5327e311e0fa1910becbff5a169fe51fd91a9c987de3bc9b643884ad
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 PowerShell T1059.001 PowerShell T1204.002 Malicious File T1071.001 Web Protocols

This XLSM file contains Excel 4.0 macros, specifically utilizing the FORMULA API to call Win32 functions. The macros are designed to download and execute a second-stage payload from a list of provided URLs. The ClamAV signature 'Xls.Downloader.Emotet03220-9941789-0' strongly suggests an Emotet family infection. The reconstructed command 'regsvr32.exe C:\Windows\SysWow64\kytk.dll' indicates the execution of a downloaded payload.

Heuristics 6

  • 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.Emotet03220-9941789-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.Emotet03220-9941789-0
  • 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 http://www.bridgewien.at/admin/9Osvbo9caA4QYishnWka/
    • http://aleph.org.ng/wp-includes/k8YwVWkrdmUM9/
    • http://automyjniafordon.bydgoszcz.pl/123/mOWZgMaL/
    • http://autoat.mx/assets/VljikBuT029PkSBfrc/
    • http://bartboutens.nl/cgi-bin/aPqSkCZXI3ueRdI/
    • http://alkautsarlampung.sch.id/belajar/WQlNleMJKoulGBUvgC9/
    • http://www.annuncisiciliani.it/app/3l1ZgVfwIEiIcGelh/
    • 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
bd1141b96e73c592d43d300feb4a2bed92034dffba7d5e49bf95a81f1348fbbc		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 4144 bytes

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