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

Static analysis result for SHA-256 dea96c8da8432540…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 9c519aca3a6cd696be4526b5b17a7c6f SHA-1: c2f61576bcf61b15865b2ad79e1e5eb27d0c97c7 SHA-256: dea96c8da84325405c405c85134fbb04b60803a73a8d7b8873f0d40f450fbbb9
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 and WinAPI strings related to downloading and executing files. Specifically, the macros utilize functions like URLDownloadToFileA and ShellExecuteA, suggesting an intent to download and run a second-stage payload. The absence of a document body means the rationale is based solely on the macro and WinAPI findings.

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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