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

Static analysis result for SHA-256 5146239d10928b39…

MALICIOUS

Office (OOXML) / .XLSM

24.2 KB Created: 2015-06-05 18:17:20 UTC Authoring application: Microsoft Excel 16.0300
MD5: 3efb0b7f7b03d20d33376aacf6863f36 SHA-1: 35e21b5033ff1d608433e43c88fd23eb5b2263ea SHA-256: 5146239d10928b39aac6e63f848dd20325001cb1a6e8aabd2338076a3f23e0e6
108 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Service Control T1204.002 Malicious File: Malicious File

This XLSM file contains Excel 4.0 macros, which are known to be used for malware delivery. The critical heuristic 'OOXML_XLM_DANGEROUS_FN' indicates the use of dangerous XLM functions like REGISTER, which can be used to call arbitrary Win32 APIs. This allows the macro to download and execute payloads without relying on VBA. The presence of hidden sheets further suggests an attempt to conceal malicious activity. No specific IOCs were extracted, but the technique is indicative of a downloader or initial access stage.

Heuristics 4

  • Dangerous XLM formula APIs: REGISTER, HALT, FORMULA.FILL 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.
  • Excel 4.0 macro sheet (1 sheet(s)) high 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.
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 7 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.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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
b7d0c28a7a68b5ffe892933497a79b65a06888c887401dd098cd6913fe79d89b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 40181 bytes

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