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

Static analysis result for SHA-256 9e34a4849b6ee4de…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: e7425e26aec8832a82b1aefbcf175e69 SHA-1: eeeb7c61e10c35e512477c95f546293bce0b5d2b SHA-256: 9e34a4849b6ee4dea2f1aa75a1f460031a5080a433510dafebafc48399f975a3
120 Risk Score

Malware Insights

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

The file contains critical heuristic firings indicating the presence of Excel 4.0 macros with WinAPI and download strings. Specifically, it references functions like URLDownloadToFileA, DownloadToFileA, and ShellExecuteA, suggesting a payload download and execution mechanism. The presence of these WinAPI calls within the macro sheet strongly implies the intent to download and run a second-stage executable. No specific family could be identified.

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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