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

Static analysis result for SHA-256 8b47d427df894247…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 433ee1abfdcfe231623b74f9f306ed64 SHA-1: 4ae91751ca0093768ff8e41afa30be94d0e70443 SHA-256: 8b47d427df894247feb9a87ff3f22893572cb3175bbbd02fcfadea6133e93b90
120 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros. Heuristics indicate the presence of WinAPI calls such as URLDownloadToFileA and ShellExecuteA, suggesting the macro's intent is to download and execute a second-stage payload. The specific WinAPI strings found are direct evidence of this download and execution behavior.

Heuristics 2

  • Excel 4.0 macro sheet (1 sheet(s)) critical 1 related finding 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
Preview script
First 1,000 lines of the extracted script
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... (truncated)