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

Static analysis result for SHA-256 3c0de77c3a6cb8c0…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: d5ff4ee08dde0d66625c7bda94e62429 SHA-1: dd69d82c8c0859a0abe4e8e88a4ea23836fce379 SHA-256: 3c0de77c3a6cb8c045babad7e7de4f3378c2bcc6e7c993285ef2cd618f39beca
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1105 Ingress Tool Transfer

The file is an Excel 4.0 macro sheet, identified by critical heuristics indicating WinAPI and download strings. The macros likely leverage functions such as URLDownloadToFileA and ShellExecuteA to download and execute a secondary payload, as suggested by the presence of these WinAPI calls and the .exe path artifact. The specific download URL and final executable path could not be fully reconstructed due to script truncation.

Heuristics 2

  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194023 bytes

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