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

Static analysis result for SHA-256 5f501dc1fea95288…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: cdd6903ba658ea2c35cdd168a4e479e9 SHA-1: 3e0ded9bc0911c12e97e7a2c825ee618e4f72e84 SHA-256: 5f501dc1fea9528856159cbcf2010de0102c49c57040e99cf0f7fb457047b018
120 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, indicated by the 'OOXML_XLM_MACROSHEET' heuristic. The 'OOXML_XLM_BINARY_WINAPI_STRINGS' heuristic further suggests these macros contain WinAPI calls like URLDownloadToFileA and ShellExecuteA, pointing to a downloader functionality. The presence of these strings strongly suggests the macro's intent is to download and execute a second-stage payload from a remote source.

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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