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

Static analysis result for SHA-256 620d5382ac0545cc…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 3c86e3e5db33751f72d44a5bf1d0ef1a SHA-1: 27b7e709d89293dfd811d452fd5a1fc94007b732 SHA-256: 620d5382ac0545cc3a162e885025920b7c96118b2829f7c57c62a5f515835d35
120 Risk Score

Malware Insights

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

The file contains Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The OOXML_XLM_BINARY_WINAPI_STRINGS heuristic further reveals the presence of WinAPI functions like URLDownloadToFileA and ShellExecuteA, suggesting the macro attempts to download and execute a secondary payload. The macro sheet is truncated, but the identified functions strongly imply a downloader or droppper functionality.

Heuristics 2

  • Excel 4.0 macro sheet (1 sheet(s)) critical 1 related finding 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
Preview script
First 1,000 lines of the extracted script
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... (truncated)

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