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

Static analysis result for SHA-256 efb916c9ef98fb62…

MALICIOUS

Office (OOXML) / .XLSX

26.3 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 28a8988468bf1089a48e9831bb9bc978 SHA-1: 1980385b1c2ab5e2b7f9e2bf961deeaaa134545a SHA-256: efb916c9ef98fb623ac72b5c0ae6b9b06d5f5fbf09b30d4e1d27eae47640a5a8
182 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros that leverage WinAPI functions like URLDownloadToFileA and ShellExecuteA. These functions are indicative of a downloader attempting to retrieve and execute a second-stage payload from the URL http://blog.africaincoming.com/ds/3.gif. The presence of these specific WinAPI strings and the embedded URL strongly suggests a malicious downloader.

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://blog.africaincoming.com/ds/3.gif

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
eaff0e08dae54ae5c2277c12a3f931b46dc9093899d9a3584bf44959199594e1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 200463 bytes

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