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

Static analysis result for SHA-256 24afdc5eec90e61a…

MALICIOUS

Office (OOXML) / .XLSX

72.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 59130955f8ce27f24e0af842e12a769c SHA-1: 16c887ef2753eb8853906395a7a5e97c9655bd4c SHA-256: 24afdc5eec90e61a909be062a613ec02eaf788cd2d9d33a1a048ec43f68c16d6
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1105 Ingress Tool Transfer

The sample contains Excel 4.0 macros that utilize WinAPI functions such as URLDownloadToFileA to download files. The macros reconstruct a path to 'C:\ProgramData\iWoLymYqHJ a' which is likely where the downloaded payload will be saved. The URLs extracted, though currently flagged as benign, are the targets for the download. The macro's intent is to download and execute a second-stage payload.

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/911259060106559531/912320486237700146/uZfSHZZlcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911259060106559531/912320572539682856/guzEocuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911259060106559531/912320453304004628/NOUkkFZlcuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
25aa5a0f2b0589600cfbbfd9a938d13b1f8503fef4e4e065ecc8e4cb1bcafb44		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5411 bytes

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