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

Static analysis result for SHA-256 21423d202df72cbf…

MALICIOUS

Office (OOXML) / .XLSX

486.6 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 595c281246f0fc0ed84f34c5bfa857c3 SHA-1: 8cfbb7311f71e2575efcf177dd0c4b9d4e6a7dea SHA-256: 21423d202df72cbfc2633af358bff81380cd2be531279debcaa665a3dc36b265
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1204.002 Malicious File

The sample is an Excel file containing Excel 4.0 macros, indicated by multiple critical heuristic firings including 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_DANGEROUS_FN'. The presence of dangerous XLM formula APIs like EXEC suggests the macro is designed to download and execute a second-stage payload. No specific family could be identified, and no external IOCs were extracted.

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 — context-specific rules above attribute URLs they actually evaluated; this rule lists URLs that were present in the bytes but were not otherwise tied to a specific finding.
    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
    • http://schemas.microsoft.com/office/excel/2006/main
    • 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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