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

Static analysis result for SHA-256 454795a72916e5bd…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 85086edbeee733a8e62ba86de9e31f23 SHA-1: 33b929d2b9624a0af438cbf84a1a5ca0a80c9d6d SHA-256: 454795a72916e5bdd16b8e820c6fc9285de476c4e14d6506716dbd966399cc0e
120 Risk Score

Malware Insights

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

This Excel 4.0 macro sheet contains strings indicative of downloading and executing a file, specifically referencing WinAPI functions like URLDownloadToFileA, DownloadToFileA, and ShellExecuteA. The presence of these functions strongly suggests the macro's intent is to download a second-stage payload from a remote source and execute it. The file is an XLSX, but the embedded macrosheet is Excel 4.0 format, a known vector for malware delivery.

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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