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

Static analysis result for SHA-256 3fe5e5d465cdf334…

MALICIOUS

Office (OOXML) / .XLSX

84.0 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: d895eb8541b63b6d80b11f66f053dc35 SHA-1: 48ca23cd4f505917f3645a1147171e826658fc24 SHA-256: 3fe5e5d465cdf3347f3e6c242dde41cffa4a53dc82999bfe912bf07ded5b0bcd
182 Risk Score

Malware Insights

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

The sample is an Excel file containing Excel 4.0 macros. These macros utilize WinAPI functions such as URLDownloadToFileA to download a file from one of the provided URLs. The downloaded file is likely intended to be executed, establishing a second stage of the attack. The reconstructed path 'C:\ProgramData\BxAywASqkXtVDH' suggests a potential location for the dropped payload.

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/911249881849536584/912356067688714250/cvVactCffEgjaSvpshekniggagook.flac
    • https://cdn.discordapp.com/attachments/911249881849536584/912356063758675998/GjEdowscAmeMpshekniggagook.flac
    • https://cdn.discordapp.com/attachments/911249881849536584/912356058922614854/CVjrWfYwLXUpshekniggagook.flac

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
3546d684c203088abe6f575e2becfd970e1a1ca889765ceb59edadb5834f2ef7		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5035 bytes

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