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

Static analysis result for SHA-256 ce7ef35724773a7d…

MALICIOUS

Office (OOXML) / .XLSX

103.0 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 8a33c8b4cae7113397ca09e56ed6a2ac SHA-1: 55648e211bc55975683c7286a105d3376b9f27ee SHA-256: ce7ef35724773a7d94a28e6a369dadd01e17aac317bc64d85c0761a46ece7ce7
250 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

This Excel file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous functions like FORMULA to call Win32 APIs, specifically 'rundll32.exe' with 'urlmon.dll' and 'DownloadToFile' and 'DllRegisterServer' functions. These functions are used to download a payload from multiple embedded URLs and likely execute it. The presence of multiple benign-looking URLs suggests an attempt to obscure the malicious destination. The ClamAV detection further confirms its malicious nature.

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: FORMULA 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: Win.Malware.Agent-9983616-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Malware.Agent-9983616-0
  • Hidden worksheet (hidden) low OOXML_HIDDEN_SHEET
    Excel workbook contains 6 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
xlm_sheet_00.xml
5a62a357cb895c98dc30b4c4c5c056eac8ac1b92bc088a5bcf20517cbcd838f8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3434 bytes
xlm_sheet_01.xml
c70a51acb5791492ef3f1e96d2217abba4360bc0964fdbbf0b281da430450073		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 908 bytes
xlm_sheet_02.xml
84b5606b26315521210c94dce2556ab11c1d4148efb57521cf114d2065ef725b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 905 bytes

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