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

Static analysis result for SHA-256 d424340df5bf7076…

MALICIOUS

Office (OOXML) / .XLSM

25.2 KB Created: 2021-03-11 11:59:01 UTC Authoring application: Microsoft Excel 16.0300
MD5: c7d04e6f667128aa991abf28821fc8bc SHA-1: e48c99f892b7939a1adca9c0373b72770b1c3755 SHA-256: d424340df5bf70761d04e78a4c0781ffcd516549b33e1e6a25abf08d516ba8c4
180 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The file is an XLSM document containing Excel 4.0 macros. The critical heuristics indicate the use of dangerous XLM formula APIs like FORMULA, which are known to be used for downloading and executing payloads. The presence of an Auto_Open defined name suggests the macros are designed to run automatically upon opening the document. No specific family could be identified, and no external IOCs were extracted.

Heuristics 4

  • 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.
  • 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.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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
c55ff9aa68818cb7bbd6a90c5f2f779b23d54454edacb57b8503e72f81de2cf5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 21268 bytes

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