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

Static analysis result for SHA-256 d402feec84387934…

MALICIOUS

Office (OOXML) / .XLSX

25.1 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 609beeb0280224b76b70603d33591149 SHA-1: b0ac57e7e190aa74caea89c5cd38f2aa171f4d1d SHA-256: d402feec84387934a4a3c75ce07fcc3bdbc9633d466a89c46102aed17d3e3bfd
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings indicative of WinAPI calls for downloading files and executing them, such as URLDownloadToFileA and ShellExecuteA. A URL, http://162.241.124.141/q/1.gif, was reconstructed from a macro cell array, strongly suggesting the macro's intent is to download and execute a second-stage payload from this location.

Heuristics 4

  • Excel 4.0 macro sheet (1 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. The macro sheet is stored as XLSB/BIFF12 binary content, which many XML-only OOXML scanners miss.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • URL reconstructed from XLM cell array (1 URL) critical OOXML_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across individual numeric cells (one ASCII charcode per cell) or inside an embedded HTA that uses VBScript Chr()/&-concat obfuscation. The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF12 record stream of every worksheet and macrosheet part and decoding RK/inline-string cells in both row-major and column-major order.
  • 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://162.241.124.141/q/1.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
7f348687a322ff0112303373edb2c858878ed1ba9e3aef350018df181f6c3d12		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 199937 bytes

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