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

Static analysis result for SHA-256 4e2ca36f04d6756f…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 610a829973cde1a5a765decdedc85e82 SHA-1: 8bec27a5dd9fbd0a8be859b64aeffafa7db27a9b SHA-256: 4e2ca36f04d6756f2745f0894c3c0b6d7bdfe924acade8062005bfc6b465a4e1
120 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. Heuristics indicate the presence of WinAPI and download strings, specifically mentioning URLDownloadToFileA, DownloadToFileA, ShellExecuteA, CreateDirectoryA, URLMon, and Kernel32. This suggests the macro is designed to download and execute a second-stage payload from a remote source. The specific URLs and executable paths are not fully extractable from the truncated script, but the intent is clear.

Heuristics 2

  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
99a6a52acb8f5c734f6d86faf89e0637a94ac99f953aa583d2658b47d2e1f9b9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 194023 bytes

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