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

Static analysis result for SHA-256 4317af65a5bcde33…

MALICIOUS

Office (OOXML) / .XLSX

74.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 12d4e299dff85f5b33c81dfd42678ae3 SHA-1: d505c4987c07a5464a870b3cc57b47d6cc48ed2b SHA-256: 4317af65a5bcde338ee82863734a64bc58d5a6d12fc64931f74926b812f28149
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 reconstructed path 'C:\ProgramData\HOzrtJyVNpA' indicates the likely location where the downloaded payload would be saved. The URLs themselves are currently marked as confirmed benign, but the macro's intent to download and execute a payload is clear.

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

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
742ba05ac98541950301f5de417480cbb05732cab73bc41be144ea400f086fe8		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 5755 bytes

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