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

Static analysis result for SHA-256 ba57549e0d73b8ab…

MALICIOUS

Office (OOXML) / .XLSX

26.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: fd2cd57df8dd9e711d77d9dfed8f4a81 SHA-1: 6dbf0cb15db7972fc4e6e9d714c0aadec907c593 SHA-256: ba57549e0d73b8ab7cacc559b7ef2b0c87aa79b4c4866ffae0d5e1b238e4483a
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings like URLDownloadToFileA, DownloadToFileA, and ShellExecuteA, indicating an intent to download and execute a file. A URL, http://eblogicx.com/ds/4.gif, was reconstructed from the macro's cell array, suggesting it's the source of the payload. The presence of these elements strongly suggests a macro-based downloader attack.

Heuristics 4

  • 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.
  • URL reconstructed from XLM cell array (1 URL) critical OOXML_XLM_CELL_ARRAY_URL
    Excel 4.0 macro sheet stages its payload URL across individual numeric cells (one ASCII charcode per cell) or inside an embedded HTA that uses VBScript Chr()/&-concat obfuscation. The reconstructed URL is invisible to literal-bytes URL extraction because it is never contiguous in the workbook stream. URLs were recovered by walking the BIFF12 record stream of every worksheet and macrosheet part and decoding RK/inline-string cells in both row-major and column-major order.
  • Embedded URL info EMBEDDED_URL
    One or more URLs were extracted from the document. The URL itself is not a detection — see the per-URL labels for which channel (macro, JS, link annotation, document body, ...) reached each URL.
    URL http://eblogicx.com/ds/4.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
66d64d4c2deccf0dfa914033e595e859412750e247798836353d5f0f3258fa91		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 197532 bytes

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