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

Static analysis result for SHA-256 7956e2201fa068f5…

MALICIOUS

Office (OOXML) / .XLSX

68.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: a3fd469017877abd8fe9fd01dc60eed5 SHA-1: 0d681a7a76a1b0e0156e407c74203475907072e8 SHA-256: 7956e2201fa068f5c0f851c58375f16fd386ba74f19c048741f8a9390295ceef
182 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros that, when executed, construct and run a command to launch mshta.exe. This command is designed to download and execute a payload from one of the provided Discord URLs, likely leading to further malicious activity. The use of XLM macros and the execution of mshta.exe are strong indicators of a downloader or initial access stage.

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/907666907405099111/907967431434186752/SMmkb.mov
    • https://cdn.discordapp.com/attachments/907662428664369166/907976355260563466/zXmjtcKgUpc.mov
    • https://cdn.discordapp.com/attachments/907666907405099111/907967362886684722/fKFjdXf.mov

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
8ab264832c5f75308a3fab8ab26b8fac4d1c05bfe4efa696c5b6c290356115c6		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 163961 bytes

Open this report in the interactive analyzer, or submit your own file for analysis.