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

Static analysis result for SHA-256 d7696a2c1ede83a4…

MALICIOUS

Office (OOXML) / .XLSX

65.3 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 391b044345cf3364ea4b7b002b676391 SHA-1: c2435ad27c247fb28843128b7a679a67c322e09e SHA-256: d7696a2c1ede83a43befcedde7c0dd6979be5c9b63554f65ce762a2159a92cb8
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic for Applications T1105 Ingress Tool Transfer

The sample contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize WinAPI functions like URLDownloadToFileA to download a second-stage payload from the provided URLs. The URLs themselves are embedded within the macro sheet, indicating their role in the attack chain. Although the URLs are currently marked as confirmed benign, the presence of the download functionality within the macros strongly suggests a malicious intent to fetch and execute further stages.

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.
  • Binary XLM macro sheet with WinAPI/download strings critical OOXML_XLM_BINARY_WINAPI_STRINGS
    Excel 4.0 macro sheet is stored as BIFF12/XLSB binary data and contains Win32 download or process-execution API strings such as URLDownloadToFileA, ShellExecuteA, or CreateDirectoryA. These strings are high-signal in XLM macro sheets and catch payload-download macros that XML-formula scanners cannot parse.
  • 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/910251809556271117/912318744573927434/ZNyYGhscuntfuck.mp4
    • https://cdn.discordapp.com/attachments/910251809556271117/912318686700924958/dkqXfnpTozcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/910251809556271117/912318764127772692/ayHpfrvQqDWqgRcuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
43ebfa27810ae87c621a7faece3f4978af4540c04f1c4bcd4bfa40e66b64b606		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5471 bytes

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