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

Static analysis result for SHA-256 ec29ebe36aee5832…

MALICIOUS

Office (OOXML) / .XLSM

33.8 KB Created: 2021-01-25 14:03:43 UTC Authoring application: 16.0300
MD5: 9bb0af2d993e4bbed30070b86d126e71 SHA-1: 23a7a5f0c406f112beefc8ce70ab178197a28b47 SHA-256: ec29ebe36aee5832b495e0db3303d9f26122a2b58e2d1d92078f9f2c31d25954
210 Risk Score

Malware Insights

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

This XLSM file contains Excel 4.0 macros, which are known to be used for malicious purposes. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM formula APIs like RETURN, which can be used to download and execute payloads. The VBA code also contains a declaration for URLDownloadToFileA, further supporting the payload download functionality. The presence of hidden sheets suggests an attempt to conceal malicious activity.

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 3 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
04653d4f70c19dc08fd54c67134a1aa8916a983c36b98af1cea0988bbde9c11c		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3487 bytes
vbaProject_00.bin
c3fc58b384befd1a26dd363f471144db14936b4e3707227c92daa227e8a6a321		 vba-project OOXML VBA project: xl/vbaProject.bin 23040 bytes
xlm_sheet_00.xml
e7f433b9b6ff773d85557baf829f63d74cdd398afd824a77b694235dc76c1c2f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 980 bytes

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