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

Static analysis result for SHA-256 adc078982da3f9a8…

MALICIOUS

Office (OOXML) / .XLSM

91.8 KB Created: 2021-02-10 13:26:45 UTC Authoring application: Microsoft Excel 16.0300
MD5: 43d3c601d1fe1abf18fe30b7ed14bd49 SHA-1: 0068ec35054b380776317cb07a85a99e96c79176 SHA-256: adc078982da3f9a8d343d51f91805ad63d4e9afd060a23f47bc5cecf293f386e
210 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

This Excel macro-enabled document (XLSM) utilizes Excel 4.0 macros, specifically the RETURN() function, to download and execute a second-stage payload. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like RETURN, which can directly call Win32 functions. The 'OLE_VBA_DOWNLOAD' heuristic further confirms the intent to download content from a URL. The presence of a VBA project and the use of URLDownloadToFileA strongly suggest a downloader functionality.

Heuristics 6

  • URLDownloadToFile in VBA critical OLE_VBA_DOWNLOAD
    URLDownloadToFile in VBA
  • 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.
  • Dangerous XLM formula APIs: RETURN 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.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains vbaProject.bin — VBA macros present
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 4 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
    • http://schemas.openxmlformats.org/markup-compatibility/2006
    • http://schemas.microsoft.com/office/spreadsheetml/2009/9/ac

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
e24bf366414181188ce56a5ac51c1e330c90af7a66995f74fe3754ea93bc4ae0		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3983 bytes
vbaProject_00.bin
6a614bb13ed7719328730cae0bc0148c738da52aa8c5230f32c030d15dd850c8		 vba-project OOXML VBA project: xl/vbaProject.bin 31232 bytes
xlm_sheet_00.xml
651826e742364c8f21717ddca46b7a8a78142ff6610372154292e191d0c6333d		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 919 bytes

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