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

Static analysis result for SHA-256 67ee8dbf0a0eb2c4…

MALICIOUS

Office (OOXML) / .XLSX

74.1 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 98aac4e50fca950d78542799800246df SHA-1: e1c2455a934aa30d64ffdd4e003b1b1e69841f2f SHA-256: 67ee8dbf0a0eb2c44975a17de770094d066785f592d85c67e6ae184afff75cff
242 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 are designed to download and execute a payload. The macro explicitly calls URLDownloadToFileA to download a file from the URL http://137.74.169.189:8080/PJ3ZQWVJPYCYDCA9A6Q2Y6YAC and then executes it using mshta. The macro also contains references to other Discord URLs, likely for alternative download sources or staging. The use of WinAPI functions and the reassembled payload indicate a downloader functionality.

Heuristics 5

  • 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.
  • XLM payload reassembled from CHAR()/split formulas critical OOXML_XLM_REASSEMBLED_PAYLOAD
    An Excel 4.0 macro sheet builds its payload inside the formula token stream by concatenating per-character CHAR() calls and string fragments, so no WinAPI name, shell command, or URL is ever contiguous in the .bin for a literal-bytes scan to find. Reassembling the formulas recovered download/execute API names, LOLBin commands (regsvr32/rundll32/mshta/wmic/powershell), or a payload URL — the de-obfuscated download-and-run kill chain.
  • 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 http://137.74.169.189:8080/PJ3ZQWVJPYCYDCA9A6Q2Y6YAC
    • https://cdn.discordapp.com/attachments/911259060106559531/912324004558278676/QpDOnpHmFcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911259060106559531/912324177363607552/NQgXTmcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/910251809556271117/912323433981935627/KGzvuEPqeCvxncuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
ca5424de22639338e0e213d50b35a3ec6de1d85c7b457fc8e7426487caf5e1c2		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5385 bytes

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