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

Static analysis result for SHA-256 e81156dcfe401213…

MALICIOUS

Office (OOXML) / .XLSX

77.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: aa3df77cd591ef5c297676a66f630c57 SHA-1: 8a3d86d81d4e5a0ffa8c595b585c45b5048dd1fa SHA-256: e81156dcfe4012131d093e08a5fd9c6e9b6b31f545b5cf337f709095650edfea
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications 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 utilize WinAPI functions like URLDownloadToFileA and DownloadToFileA to fetch and execute a payload from a provided URL. The reconstructed URLs point to executable content, indicating a downloader or droppper functionality. The specific URLs are flagged as confirmed benign, but the macro functionality itself is indicative of malicious intent.

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 (3 URLs) 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 https://cdn.discordapp.com/attachments/910251809556271117/912318814543282226/cGrqSnWcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911261535769362435/912322627044012032/JICgBzlnZfFKaXpcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911261535769362435/912322704428892190/YrSGHhXTrGUNcuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
1d36c0cabc8d1000037b87ca4ab010d478089f866880b5d0f0e583e500f1999f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5257 bytes

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