Emotet — Office (OOXML) / .XLSM malware analysis

Static analysis result for SHA-256 3a3ddc0c2f850b7a…

MALICIOUS

Office (OOXML) / .XLSM

21.2 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300 First seen: 2022-03-16
MD5: 4fef7c6b50b635dd0823a1e4aa0abafd SHA-1: d014d9f9fab46a00e9c506a8e4f0d15a2eac4b37 SHA-256: 3a3ddc0c2f850b7ad301f4187acfc80101d8c8c4d3397753d14cc9bc649ec2d3
250 Risk Score

Malware Insights

Emotet · confidence 95%

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1059.001 Command and Scripting Interpreter: PowerShell T1204.002 Malicious Link: Malicious File T1105 Ingress Tool Transfer

The file is an Excel 4.0 macro sheet (XLSM) that uses the dangerous FORMULA API to download and execute a payload. The macro constructs a command to download a file named 'rfs.dll' and then execute 'regsvr32.exe' with it, likely to load a second-stage payload. The ClamAV detection as 'Xls.Downloader.Emotet03220-9941789-0' strongly suggests the Emotet family. Multiple malicious URLs were extracted and used in the download process.

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://astroadvicebaba.com/assets/jYlBTPcWJTsTtamDfX/
    • http://orchidbg.com/aeeiludqootr/OcnjiLHL/
    • http://snappylookphotobooth.com/headers/P/
    • http://casadorothea.com/cc/H5v/
    • https://physioacademy.co.uk/conditions/8I3WSx5t2k/
    • https://westthamesphysio.com/blog/3tsZIz09Sox1Z/
    • http://194.59.165.91/nbproject/1XFiatvBCRW9eh5JxptS/
    • 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
f9ef0dd03a642623a126a648a3e3b498d8403d13558799b8b55ca81a239f78e5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3968 bytes

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