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

Static analysis result for SHA-256 6835f285bf5a6d6a…

MALICIOUS

Office (OOXML) / .XLSX

486.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 845eee0cb27bfe67313cd8e7821357b0 SHA-1: 0c466cd46eb4162c66f1193f1122a7f9e0f9668f SHA-256: 6835f285bf5a6d6ae72794eca298eff63f2095a31d7c94b4626634fb2ec49f9d
250 Risk Score

Malware Insights

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

The file contains critical heuristic firings indicating the presence of Excel 4.0 macros, specifically using dangerous functions like EXEC and GOTO. These functions are often used to download and execute secondary payloads. The ClamAV detection further supports its malicious nature. The specific macro commands suggest an attempt to execute external code, likely a downloader.

Heuristics 6

  • Excel 4.0 macro sheet (3 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: GOTO, EXEC, 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.
  • ClamAV: Xls.Downloader.GreenEnable06210-9869360-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Xls.Downloader.GreenEnable06210-9869360-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 4 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 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.xml
3b0842c3feb9ed67b33a34a48dfc280d3096f5a2c314be3f5faf78e2baa667ed		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1648 bytes
xlm_sheet_01.xml
3d2b487a4797c3e753fa6529eda083e6797d4efab8dc0fa1c702e5900b8f7621		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1807 bytes
xlm_sheet_02.xml
2b4b5b0b53ce73defaa76ed337ef97cab4ed7333ba343720c48a9f6682388bd1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet3.xml 2260 bytes

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