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

Static analysis result for SHA-256 b64cf6500def09c4…

MALICIOUS

Office (OOXML) / .XLSM

35.0 KB Created: 2021-03-01 13:56:52 UTC Authoring application: Microsoft Excel 16.0300
MD5: f0851910c4601259111fb4a59cd02713 SHA-1: f9e827f5e99d5475534c3d4d4a800695b82f1510 SHA-256: b64cf6500def09c4187c04918c26665e89d41ceccef485da63abb76b05e70c89
210 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros that leverage the `RETURN()` function, which is a known primitive for executing arbitrary code. The VBA script includes a call to `URLDownloadToFileA`, indicating an intent to download and execute a second-stage payload from a remote source. The presence of hidden sheets and the use of dangerous XLM formula APIs further support this malicious intent.

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 1 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
90e1029031be36f6f97a4d72c7f1ec04b43723f2c7594055be366751595e6e45		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 2722 bytes
vbaProject_00.bin
fda8be90d354b50c53685a7776f4cca1bd13fd13015649f86eab62c72ab12b11		 vba-project OOXML VBA project: xl/vbaProject.bin 20480 bytes
xlm_sheet_00.xml
a39fa49e98e85e4cbb4d343028f030569c7f524f7caef108df9b23443dd6e131		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 968 bytes

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