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

Static analysis result for SHA-256 fb044e7ea2cc643b…

MALICIOUS

Office (OOXML) / .XLSX

102.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 3b4b02112daac50f51a327f92c6d4e3d SHA-1: 4d2049f5025e36670a4d07a39598f6f277d6efc6 SHA-256: fb044e7ea2cc643b200355816314ae5cc290939aefdaa932939337a300cc9263
290 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1218.011 System Binary Proxy Execution: Rundll32 T1105 Ingress Tool Transfer

The sample utilizes Excel 4.0 macros, specifically leveraging dangerous functions like FORMULA to execute arbitrary code. The extracted DOC BODY content shows a clear attempt to use 'rundll32.exe' with 'urlmon' to download a file from one of the provided URLs. This indicates a downloader or initial access stage for a larger attack. The use of Excel 4.0 macros and the specific execution chain points to a sophisticated, albeit older, technique for initial compromise.

Heuristics 7

  • 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-9991551-0 critical CLAMAV_DETECTION
    ClamAV detected this file as malware: Win.Malware.Agent-9991551-0
  • LOLBin token sequence in document text high SE_LOLBIN_RUN_COMMAND
    Extracted document text contains a Windows script/execution tool name (PowerShell, mshta, cmd, rundll32, regsvr32, …) within 220 characters of a dangerous flag, command verb, or URL. This is a visible 'run this' instruction in HTML/PDF/RTF lure bodies, or — in macro-laden Office files — the macro's own string-pool entries appearing adjacent in extracted text.
  • 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://docs-construction.com/wp-admin/a0mJP2Adw5YTHt/
    • http://centrobilinguelospinos.com/wp-admin/EIzEADnvS/
    • http://laohange.com/wp-content/0qJRIjTThZ/
    • http://stancewheels.com/wp-admin/b5xkQkgEFiBmW/
    • http://jeffreylubin.igclout.com/wp-admin/0WGa0yF6b6F3VK5tb/
    • 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
70a630ebf16b860ac1225608b3179a268dffdcabbd610f9adf303328d4dd015b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/intlsheet1.xml 3567 bytes
xlm_sheet_01.xml
5de2d301cc109db6d36eebc969e56f919066258ce8b719219c5af3a6383fbd2a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.xml 1277 bytes
xlm_sheet_02.xml
1f318126f9836ee0e7eb4db4c3253b3f492929ce10b9e2356f4d0da8bf32f74a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet2.xml 1152 bytes

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