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

Static analysis result for SHA-256 aad29b6eff197e7c…

MALICIOUS

Office (OOXML) / .XLSM

108.4 KB Created: 2021-03-22 13:06:06 UTC Authoring application: Microsoft Excel 16.0300
MD5: 7abead803cb0b269441153efda6813c3 SHA-1: a97364a28c4318dad3c4f85e68d1ae8b95b7ab19 SHA-256: aad29b6eff197e7c7da88761b20d732733d1caca1f803558db8b9e4feb9d9a7d
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 file is an XLSM document containing Excel 4.0 macros. Critical heuristics indicate the use of dangerous XLM formula APIs like 'RETURN' and 'URLDownloadToFile', suggesting the macro is designed to download and execute a second-stage payload. The presence of hidden worksheets further supports the concealment of malicious activity. No specific family could be identified, but the technique is common for initial payload delivery.

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
9f6541a1a6131a1509c55dca80a9f16215d8f88fb80aa0f778f2d1e656715f16		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3185 bytes
vbaProject_00.bin
0d27c8dbd17f8789983c974b119d4a641278c47567b676fe8ac8d35a364c66ea		 vba-project OOXML VBA project: xl/vbaProject.bin 23040 bytes
xlm_sheet_00.xml
a2b109cf24a1f89e5ba7eba83944827bf4dd008d2c7ceca1492870bd1ee86e02		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 913 bytes

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