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

Static analysis result for SHA-256 c53a4e6e150f0422…

MALICIOUS

Office (OOXML) / .XLSX

72.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 7d73cea1825c8364f7f70e791a538a63 SHA-1: 5c58594f8308541ebc3254bf934e5b804212eb10 SHA-256: c53a4e6e150f0422c998d6a91fa92a16962b68b65852c99a0c87af101729fb62
182 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros that utilize WinAPI functions such as URLDownloadToFileA to download a file from one of the provided URLs. The macro sheet also contains strings that appear to be part of a path within the ProgramData directory, suggesting an attempt to save the downloaded payload. The URLs themselves are marked as confirmed benign, but the macro's intent to download and execute is clear. The macro sheet was truncated, preventing a full analysis of the execution flow.

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/911261535769362435/912322756757061693/KkFbocuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911261535769362435/912322613773213726/uFLOSFulSRDWZcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911259060106559531/912320486237700146/uZfSHZZlcuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
b46c348e46a41cd761db21680fc853af4a37dfc4cec0fa557371f05dd2f837a5		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5877 bytes

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