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

Static analysis result for SHA-256 c88b279519d1708a…

MALICIOUS

Office (OOXML) / .XLSX

102.4 KB Created: 2015-06-05 18:19:34 UTC Authoring application: Microsoft Excel 16.0300
MD5: 123c33beac81acfaf0bea25939456965 SHA-1: 14e33c0f93321446b94129dca3e39d5f131b706b SHA-256: c88b279519d1708a9adbcff9340a309e7c257149f530e62380d7cd7cccff9e6d
290 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize dangerous XLM formula APIs like FORMULA to call external functions. Specifically, it constructs a command to execute 'rundll32.exe' with arguments that download a file from one of the provided URLs. The reconstructed command is 'rundll32.exe SysWow64\..\iix.ocx,URLDownloadToFile'. This indicates the macro's intent is to download and execute a second-stage payload.

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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