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

Static analysis result for SHA-256 fd81c88039e48a1c…

MALICIOUS

Office (OOXML) / .XLSM

25.0 KB Created: 2021-03-11 11:20:03 UTC Authoring application: Microsoft Excel 16.0300
MD5: 724290f49e016fd2d5bd84396f9bba85 SHA-1: e07802321d84cc1c601615318f6eef6ec90366d4 SHA-256: fd81c88039e48a1c9eb2d87d2e8736bf07a19ec798832cc149928bb018b700b9
180 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, specifically utilizing the dangerous FORMULA API. This indicates the macro is designed to call external Win32 functions, likely to download and execute a secondary payload. The presence of an Auto_Open defined name further suggests automatic execution upon opening the document. No specific family could be identified, and no direct IOCs like URLs or hashes were extracted from the macro content itself.

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
29fc1a63979172bab49b2a3bd7a5679a64ec765995777e6aabccd3f13c5b7041		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 20072 bytes

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