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

Static analysis result for SHA-256 a26be10f2a6b75f3…

MALICIOUS

Office (OOXML) / .XLSX

24.7 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: faff843af22ed72eda794788230e5280 SHA-1: 5494f26788021b9c3a4d585742386b78861feda9 SHA-256: a26be10f2a6b75f384c55d1f60d18f3db3c2cd5b5e7a75c4049ecb639a7050f0
182 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings related to WinAPI functions such as URLDownloadToFileA, DownloadToFileA, and ShellExecuteA, indicating an intent to download and execute a payload. The reconstructed URL http://162.241.115.60/q/1.gif is likely the source of this payload. The presence of these functions and the embedded URL strongly suggest a downloader attack pattern.

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://162.241.115.60/q/1.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
88bbfd9c46e480ac4f7ac203afcf9ebcf31b2422c88e27a92bef8993e8f14c40		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194725 bytes

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