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

Static analysis result for SHA-256 a2d6fdfe43af7675…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 4e20a72427d376966c7b411b82e5d5dc SHA-1: d91c86853fa1e2288bdff2a233122b54ed991318 SHA-256: a2d6fdfe43af76757da8c145c15333f7f11d3d2eccad41ab1b399320c5739879
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 an Excel 4.0 macro sheet, which is highly suspicious. Heuristics indicate the presence of WinAPI and download strings such as URLDownloadToFileA, DownloadToFileA, and ShellExecuteA, suggesting the macro's purpose is to download and execute a second-stage payload. The macro sheet is truncated, preventing full analysis, but the identified functions strongly imply malicious intent.

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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