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

Static analysis result for SHA-256 a4dc3c7bca9601bf…

MALICIOUS

Office (OOXML) / .XLSM

16.8 KB Created: 2020-11-13 07:54:05 UTC Authoring application: Microsoft Excel 16.0300
MD5: 98bf77e681e28286e129381832cf83be SHA-1: 1baf3c700a4ec774c474d97c10dd656ded2a1040 SHA-256: a4dc3c7bca9601bf642e6df0f9baea765a78265fdd20a5bb0aec36ab488dc278
100 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The critical heuristic firing indicates the use of dangerous XLM formula APIs like RETURN and HALT, which can be leveraged to download and execute arbitrary code. While no specific URLs were extracted from the document body or scripts, the presence of these dangerous functions strongly suggests a downloader or initial execution stage for a more complex attack. The confidence is high due to the direct use of dangerous XLM functions, but the family is unknown as no further payload indicators were found.

Heuristics 3

  • Dangerous XLM formula APIs: RETURN, 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.
  • Excel 4.0 macro sheet (1 sheet(s)) high 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.
  • 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
f78f7a7fd8fdd36a91405c423856218f250fbdbd0a14bc65fc353f1782a417ff		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 10523 bytes

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