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

Static analysis result for SHA-256 5e968141f1cca2b2…

MALICIOUS

Office (OOXML) / .XLSX

117.3 KB Created: 2020-06-23 11:38:23 UTC Authoring application: Microsoft Excel 16.0300
MD5: 1fd23cc4440ffb33ac83d4d75cbdaddd SHA-1: fa814c7479dda0d54cbea0abe3d08880452cbf42 SHA-256: 5e968141f1cca2b2a776462b887ca1ab7fdbb65a4c80bbc229902b2bfcd62351
210 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file is an Excel spreadsheet containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The macros utilize dangerous functions such as REGISTER, FORMULA, CALL, and EXEC, which are known primitives for downloading and executing arbitrary code. The presence of a defined name 'Auto_Open' suggests an attempt to automatically execute these macros upon opening the document, and the 'SE_ENABLE_LURE' heuristic indicates a user-facing prompt to enable macros. The specific payload or download URL is not directly visible in the provided evidence, but the macro functions strongly suggest a downloader or initial execution stage.

Heuristics 6

  • 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.
  • Excel 4.0 Auto_Open defined name critical OOXML_XLM_AUTOOPEN_DEFINEDNAME
    Workbook defines _xlnm.Auto_Open or _xlnm.Auto_Close while containing an XLM macro sheet. This is the OOXML/XLSB auto-execution shape for Excel 4.0 macros.
  • Dangerous XLM formula APIs: FORMULA.FILL, REGISTER, HALT 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.
  • Macro/content-enable lure medium SE_ENABLE_LURE
    Document instructs the user to enable macros or editing — a common technique used by malware droppers to bypass Office macro security settings
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 28 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
    • http://schemas.microsoft.com/office/spreadsheetml/2014/revision
    • http://schemas.microsoft.com/office/spreadsheetml/2015/revision2
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision3
    • http://schemas.microsoft.com/office/spreadsheetml/2016/revision6

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
6f4aed1ae96430b09ce4437ce30fffe68b891f4c121f1aa8abf5bd208f469115		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 166393 bytes

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