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

Static analysis result for SHA-256 1373c715021c53a4…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 000caeede68565ab949a7e740d854b3f SHA-1: 27cc22ab9ca755a25aeaaf27ebfd92db54decf4c SHA-256: 1373c715021c53a4745daa2f177f302c499581439a3425239fc055b584131b64
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1203 Exploitation for Client Execution

The file contains embedded Excel 4.0 macros, which are known to be used for malicious purposes. The heuristics indicate the presence of WinAPI and download strings such as URLDownloadToFileA and ShellExecuteA, suggesting the macro's intent is to download and execute a secondary payload. The specific URLs or executable paths are not fully discernible due to truncation, but the presence of these functions strongly points to a downloader or dropper functionality.

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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