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

Static analysis result for SHA-256 0e87b0f3a997a984…

MALICIOUS

Office (OOXML) / .XLSX

92.0 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: f8148e0bad6d907f92008218a0296d8d SHA-1: 782f3892983c1659a101b3cf298b01d12c593ab9 SHA-256: 0e87b0f3a997a98409244e36b7da5eb04dc606b135dd9871ce39df554559f0dc
182 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros that are designed to execute a command. This command uses 'wmic' to download a file from the URL http://7.28.2:880/Q2W5VWUFL5VCM7JETCCTYX7Z4RDGC and save it as C:\ProgramData\HIXhYv.; uronRLDowloadToFileAJJCCJJhttp://7.28.2:880/Q2W5VWUFL5VCM7JETCCTYX7Z4RDGC:C:\ProraDatauLbhw.tx, likely to execute a second-stage payload. The macros also reference other Discord CDN URLs, which may be alternative download locations or related infrastructure.

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 http://7.28.2:880/Q2W5VWUFL5VCM7JETCCTYX7Z4RDGC
    • https://cdn.discordapp.com/attachments/912720368844824620/913070674094993449/ZYuTHyellowfacebrownietacohead.ogg
    • https://cdn.discordapp.com/attachments/912720368844824620/913070650476863508/wLsbzyellowfacebrownietacohead.ogg
    • https://cdn.discordapp.com/attachments/912720368844824620/913070662611001354/PMvHwqyellowfacebrownietacohead.ogg

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
6ff0f075e51264a3d635632d63cc9db1e802c5450af6345269739c771d49feb1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 7344 bytes

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