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

Static analysis result for SHA-256 3f4632f072dca5d7…

MALICIOUS

Office (OOXML) / .XLSM

111.9 KB Created: 2021-03-22 11:36:36 UTC Authoring application: Microsoft Excel 16.0300
MD5: 0c786f85bc858c5ca79fb817986c3714 SHA-1: 498f0c79fa8d3f3624b463dfec62f85ce15068e1 SHA-256: 3f4632f072dca5d71e765dcdb19f411d30a2609850ecd7234e550da2475cd925
208 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1059.005 Visual Basic for Applications T1204.002 Malicious File 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' and 'URLDownloadToFile', suggesting the macro is designed to download and execute a second-stage payload. The presence of hidden sheets further supports the concealment of malicious activity. No specific family could be identified.

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
233779d71159e426b677df69a0c7cbc8ab87dc99fed4d622fea48e3f27101362		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 3172 bytes
vbaProject_00.bin
6376e955c3c7d8e62bc8348274a47590eb6b9a6004f453b317b295b2a888d6d3		 vba-project OOXML VBA project: xl/vbaProject.bin 22016 bytes
xlm_sheet_00.xml
4c1026a69949374faa28fb5b20d111b5bede070798399343e2249f776f1e0856		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 985 bytes

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