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

Static analysis result for SHA-256 b31f7d69c5013076…

MALICIOUS

Office (OOXML) / .XLSM

25.2 KB Created: 2021-03-11 11:11:42 UTC Authoring application: Microsoft Excel 16.0300
MD5: 5b07166d4e9d0452250371025dc303c3 SHA-1: c6d2a19e6f83d20978332db21c56e7f15c8647f4 SHA-256: b31f7d69c5013076e4fcc11937e243087ac6e7b2deace9c055b4397d45634905
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 heuristics indicate the use of dangerous XLM formula APIs like FORMULA, CALL, and EXEC, which are commonly used to download and execute arbitrary code. No specific URLs or hashes were extracted, but the presence of these dangerous functions strongly suggests a downloader or dropper functionality.

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
c50858ebde96f6daa3a8ced9bd92ea713fa1661f08a9a4fadefc067fbe451ebe		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 20891 bytes

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