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

Static analysis result for SHA-256 88e4e9c99da217be…

MALICIOUS

Office (OOXML) / .XLSX

26.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 118b42203486655f01f6b98ba8375d80 SHA-1: 2387a2117d718c30c45ec97a83b207ced36efbd9 SHA-256: 88e4e9c99da217be3255a37e38daee0aee6863e911d9fd6ef7b8831391b5e04d
182 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Visual Basic T1204.002 Malicious File: Malicious File T1059.001 Command and Scripting Interpreter: PowerShell T1059.003 Command and Scripting Interpreter: Windows Command Shell

The file contains Excel 4.0 macros, which are known to be used for malicious purposes. The macros contain strings related to WinAPI functions such as URLDownloadToFileA and ShellExecuteA, indicating an intent to download and execute a payload. The reconstructed URL https://kacedu.in/ds/4.gif is likely the source of this payload. The presence of these functions and the embedded 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 https://kacedu.in/ds/4.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
4d3267d5cb48a24d8d5a76370a2eebaf0d0fae662a1ae41551cbc28e948767c7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 197524 bytes

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