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

Static analysis result for SHA-256 1dc26f4278180169…

MALICIOUS

Office (OOXML) / .XLSX

69.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: bcd5b6603b7a11c3dfb9d451111fdb27 SHA-1: 47b00e136d9e221852af570c1b947efd07675eb8 SHA-256: 1dc26f427818016973da1683e3dc5e9438303b1056292f8404ec860e398c11cd
182 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros that utilize WinAPI functions like URLDownloadToFileA to download a file. The macro reconstructs a path 'C:\ProgramData\jPpOcjQfbCFE' which is likely where the downloaded payload will be saved. The URLs extracted, although marked as confirmed benign, were referenced by the macro, indicating an attempt to fetch a second-stage payload. The use of Excel 4.0 macros and WinAPI calls for downloading external content is characteristic of macro-based malware droppers.

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/911261535769362435/912322796527427654/nGZqhzcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911261535769362435/912322749471526962/hGhlHJmcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911261535769362435/912322708434481172/YIQFLgQsQkDFcuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
1b0ee3f7d13c7c2bcbcdcbcbf162b44457d783232b27a07b11b2493c05e60888		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 4931 bytes

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