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

Static analysis result for SHA-256 25223d86aa463b8b…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 66455911f22bb19b09beb5a3f3f63601 SHA-1: e684caf6821a816b7482d357a0ad144ba1a8f213 SHA-256: 25223d86aa463b8ba5ea917a034c4bff7c67e0983704885e3c4eed7bbc7eea3f
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The sample is an Excel file containing Excel 4.0 macros. Heuristics indicate the presence of WinAPI calls related to downloading and executing files, specifically URLDownloadToFileA and ShellExecuteA. This suggests the macro is designed to download and run a secondary payload from a remote source. The specific WinAPI strings found are URLDownloadToFileA, DownloadToFileA, ShellExecuteA, CreateDirectoryA, URLMon, and Kernel32.

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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