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

Static analysis result for SHA-256 ca4010b0b7e840ae…

MALICIOUS

Office (OOXML) / .XLSX

116.0 KB Created: 2020-05-11 14:19:29 UTC Authoring application: Microsoft Excel 16.0300
MD5: c5a179c6fe1f057c380e64ad5a5151f1 SHA-1: 4b4c23004dab867b6759a921a24cfa181167ea62 SHA-256: ca4010b0b7e840aed10f2439fc37429aa7c752cf8c312d5c3de01b3342dd69fb
202 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File T1059.001 PowerShell T1105 Ingress Tool Transfer

This XLSX file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros utilize WinAPI functions such as URLDownloadToFileA, DownloadToFileA, and ShellExecuteA to download and execute a payload from the URL http://phod.ru/image1.png. This indicates a downloader or droppper attack pattern.

Heuristics 5

  • 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.
  • VBA project inside OOXML medium OOXML_VBA
    Document contains vbaProject.bin — VBA macros present
  • 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://phod.ru/image1.png

Extracted artifacts 3

Files carved from inside the sample during analysis.

FilenameKindSourceSize
macros.bas
db936188ce187fdfb8ca7c90576df4211946ce9bab4ac7b23e1845d864c775fd		 vba-macro oletools.olevba.extract_macros (decoded VBA source from OOXML) 6475 bytes
vbaProject_00.bin
f42e221ad1e4addbee388a94235b985f80b6a4fecb0fdc44c9fd476fc89558ce		 vba-project OOXML VBA project: xl/vbaProject.bin 43520 bytes
xlm_sheet_00.bin
068d13e4f3fd3362b2c3b76fd8b00a36c1376692c6333c6d9a127b9d90e8d10f		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 51208 bytes

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