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

Static analysis result for SHA-256 9c514397c74437d1…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 34b0d0520b65ffe104490b740cfa5843 SHA-1: c86314d1f0dd5f2aad8a666eeda071be1c65c792 SHA-256: 9c514397c74437d1e323e4b5b4d053d83997d8d44255ccc5b06756586bb767f2
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, DownloadToFileA, and ShellExecuteA, suggesting the macro's intent is to download and execute a secondary payload. The macro sheet itself is large, implying complex functionality, and the presence of WinAPI strings related to file operations and execution points to a downloader or dropper.

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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