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

Static analysis result for SHA-256 12eaf951c99536e7…

MALICIOUS

Office (OOXML) / .XLSX

180.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: c429449c26cfd371956049a1764e33d5 SHA-1: be630c93bea7edd5cbe0eeac259747e3452ee05c SHA-256: 12eaf951c99536e73590646abe3c82ced0e9c7a0e475ac3138884ba977fa2549
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution T1105 Ingress Tool Transfer

The sample contains Excel 4.0 macros that are designed to download and execute payloads from the provided Discord URLs. The macro logic reconstructs a command to execute 'mshta' with a specific file path, indicating a likely attempt to download and run a second-stage malicious file. The use of XLM macros and the download mechanism points to a downloader or droppper 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) 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/910880417756901430/914825094277238794/TqczOmniggerfuckburnjew.nigga
    • https://cdn.discordapp.com/attachments/910880417756901430/914825062333427732/RWjNozEzaUCyainiggerfuckburnjew.nigga
    • https://cdn.discordapp.com/attachments/910880417756901430/914825130243391498/xCHubAkCgPIqmniggerfuckburnjew.nigga

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
d51ba0207a12061785e5a51d9c627012a6dea6db0b18624da080dd910dcdc68f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 3896 bytes

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