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

Static analysis result for SHA-256 da4043586d9cbbf6…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 380dcc317b810f426eaf16dd253cbc5c SHA-1: 60458650d66b5d428ae4392f394548465dc973c1 SHA-256: da4043586d9cbbf675812b2f86fa5aac6eb1bd22250a6316cbc1a71941c08a93
120 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic 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 calls related to downloading files and executing them, specifically URLDownloadToFileA, DownloadToFileA, and ShellExecuteA. This suggests the macro is designed to download and execute a second-stage payload from a remote location. The specific WinAPI strings found are the primary indicators for this analysis.

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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