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

Static analysis result for SHA-256 85cebd2f3ed53d4e…

MALICIOUS

Office (OOXML) / .XLSX

74.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: e62314e4af437ffd1b9f27bc0cd817ed SHA-1: c8a505bef50c361ae43da6b200e921f814fbe321 SHA-256: 85cebd2f3ed53d4e52ea415cfdb52bffb74710d9d0ee3516a55880ed8aab99ac
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 reconstruct a command line to download a payload from a Discord URL. The macro logic appears to be designed to execute a second-stage payload, likely using 'wmic ocess cal creatsha C\ProgramData\LppS.rt', which is indicative of a downloader or dropper malware.

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), inside an embedded HTA that uses VBScript Chr()/&-concat obfuscation, or split across multi-char fragment cells a download formula concatenates by reference (=A1&A2&… / CONCATENATE(...)). 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/shared-string cells in row-major and column-major order plus FORMULA cell-reference concatenation in token 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/912726182980624406/913011980036616192/LWGHEbeanerwopnigga.ogg
    • https://cdn.discordapp.com/attachments/912726182980624406/913011988488151071/VREcGZRvOYEWbeanerwopnigga.ogg
    • https://cdn.discordapp.com/attachments/912726182980624406/913011996872552468/sjAPKtporrJZCRbeanerwopnigga.ogg

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
51f2e5ebd01c814f4854da5f81a36e206f2d2dd2633b5e1367f8f7a62659c707		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 7189 bytes

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