Malicious Office (OOXML) / .XLSM — malware analysis report

Static analysis result for SHA-256 34b37c76248658d2…

MALICIOUS

Office (OOXML) / .XLSM

269.7 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000
MD5: c576254df1035c7729cf259c72dcf023 SHA-1: 91d21c84e0df76772cf060c3d099a122cef4116e SHA-256: 34b37c76248658d208da1630b2d9ce36147ad34c7caa1ccd2d2abd00191beaa8
190 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell T1059.003 Windows Command Shell

The sample is an Excel 4.0 macro-enabled spreadsheet. Critical heuristics indicate the use of dangerous XLM functions like EXEC and FOPEN, which are often used to download and execute payloads. The macro constructs the path 'C:\ProgramData\oMKsSOVzsVUJOA.sct', suggesting it attempts to write and execute a script from this location. The Auto_Open defined name further indicates automatic execution upon opening.

Heuristics 5

  • 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: FOPEN, FWRITE, FCLOSE, EXEC, HALT 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.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 1 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://schemas.openxmlformats.org/spreadsheetml/2006/main
    • http://schemas.microsoft.com/office/excel/2006/main
    • http://schemas.openxmlformats.org/officeDocument/2006/relationships

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
9ab68d0c85d06aa139e1bfea132e449b1521221e480bc8c584e0ec3fdd52bfd8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 876109 bytes

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