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

Static analysis result for SHA-256 4d62ad444cdbdd70…

MALICIOUS

Office (OOXML) / .XLSX

26.3 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 3f47fb2668363296eb9d3adb9566508f SHA-1: e6846bbd697c1d44fecd59a9d5c1b827823e829c SHA-256: 4d62ad444cdbdd702294cd6cb985003497b7495f6b7b887518ea4eba441dec59
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1059.003 Windows Command Shell T1059.004 Unix Shell

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings related to downloading files and executing them, such as URLDownloadToFileA, DownloadToFileA, and ShellExecuteA. The macro reconstructs the URL http://puroraw.com/ds/3.gif, which is likely used to download a second-stage payload. The presence of these strings and the reconstructed URL strongly suggest a downloader attack pattern.

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://puroraw.com/ds/3.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
bcb2a00478b552ea7aa0ba3395a02a282bd76772458f85092b2d3253d326ab01		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 200414 bytes

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