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

Static analysis result for SHA-256 1619d83c7c87ff0a…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: f0c1b6b6fc628869dd4ac26258d99efb SHA-1: d88100f90907d742702e9d1107bade21c3a27c2b SHA-256: 1619d83c7c87ff0af1c3bba2c0050a53d23293f0e48109971a41fb8ba18563cb
120 Risk Score

Malware Insights

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

The file contains embedded Excel 4.0 macros, which are known to be used for malicious purposes. The heuristics indicate the presence of WinAPI calls such as URLDownloadToFileA and ShellExecuteA, suggesting the macro attempts to download and execute a second-stage payload. The specific URLs or executable names are not directly visible in the provided evidence, but the intent to download and run a file is clear.

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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