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

Static analysis result for SHA-256 63ce1d00cc40a787…

MALICIOUS

Office (OOXML) / .XLSX

69.0 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: c2c827e43ca3d3452180dd36bc52b582 SHA-1: a922d550d0d0af0434d71fe2066417d1ff82f2c3 SHA-256: 63ce1d00cc40a7870cff0f8256f54b786255f9928e6c9747d4fb7c3fb83ba278
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

This Excel file contains Excel 4.0 macros that are designed to download and execute a payload. The macro uses a CHAR() and split formula to reassemble a command that executes 'wmic process call cratemsha C:\ProamData\RrdQqFVxs.rtf' and downloads a file from 'http://158.140.185.205:808/QW5VUFL5VMQ7JQPETG3CCYX72Z4R25P' to 'C:\Pogramata\DirrSxDpqK.xt'. The URLs extracted from the cell array are likely alternative download locations for the 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.
  • 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 https://cdn.discordapp.com/attachments/912720368844824620/913069632129212466/reSCeFOYjZtCtkOyellowfacebrownietacohead.ogg
    • https://cdn.discordapp.com/attachments/912720368844824620/913069652077326346/KftJXyrZQyellowfacebrownietacohead.ogg
    • https://cdn.discordapp.com/attachments/912720368844824620/913069669341069452/jPzSCuyellowfacebrownietacohead.ogg

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
e71aa2ac306ab40d8f3332b9e787633e5a98c65091ffd44ae83849d67249e647		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 7457 bytes

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