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

Static analysis result for SHA-256 485f60ab0f9bc836…

MALICIOUS

Office (OOXML) / .XLSM

179.4 KB Created: 2021-03-22 13:11:24 UTC Authoring application: Microsoft Excel 16.0300
MD5: d6c84d6b5daaa8f8c6e751b2a3f3bee2 SHA-1: bbd162a3c1762334d675b1ea9335677e6b3ae75e SHA-256: 485f60ab0f9bc836dc2c7e855583c1ec230bf44eebd8c6ae9ab03cb7efb15d42
208 Risk Score

Malware Insights

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

The sample is an XLSM file containing Excel 4.0 macros. Heuristics indicate the use of dangerous XLM formula APIs like RETURN, which are often used to download and execute payloads. The presence of URLDownloadToFile in VBA further supports this. The document body is heavily obfuscated and does not provide clear user-facing content, but the macro functionality strongly suggests a downloader or initial access mechanism.

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 2 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
5a3997978934809352c1dc300bc4191fa09e8c004c415fd7c54141ee0c3c9585		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3186 bytes
vbaProject_00.bin
306f5aa14c0cf4b3934dfaab426e19062fbe8e663aacd3818bbc496e11360d1d		 vba-project OOXML VBA project: xl/vbaProject.bin 22016 bytes
xlm_sheet_00.xml
a2b109cf24a1f89e5ba7eba83944827bf4dd008d2c7ceca1492870bd1ee86e02		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 913 bytes

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