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

Static analysis result for SHA-256 ec5ed6ddcdd6f8b3…

MALICIOUS

Office (OOXML) / .XLSX

79.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 39a725f8bc90efa5d8a6d90be441b120 SHA-1: ca2ed017a4e19eb5a6d3ba1d00a598548d27df59 SHA-256: ec5ed6ddcdd6f8b3e1abccb7bd0fe26d5d7d10767dcdeca18dd95591afb4fde6
182 Risk Score

Malware Insights

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

The sample contains Excel 4.0 macros that utilize WinAPI functions such as URLDownloadToFileA to download a file to 'C:\ProgramData\MXsAZZSMvSTVyEV'. The reconstructed URLs point to executable files, indicating the macro's intent is to download and execute a second-stage payload. While the URLs themselves are marked as benign, the presence of macro code designed for downloading and the specific file path suggest a malicious intent.

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 (3 URLs) 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://cdn.discordapp.com/attachments/910251809556271117/912318576080326666/LNAMxcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/910251809556271117/912318586142461974/BXyJKLCohcuntfuck.mp4
    • https://cdn.discordapp.com/attachments/911261535769362435/912322618651185203/BYsNRHlafaeAcuntfuck.mp4

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
feefa2126c6e9104c6d4ba87224c4103bbe96c9634feafc819628532946ca62b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5047 bytes

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