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

Static analysis result for SHA-256 0e7e21b7b84e124b…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: 4a7511c2b58a21131ac9751096a3be14 SHA-1: 9e0dc8fdf3f8638da79c282fa10f49665f08ea23 SHA-256: 0e7e21b7b84e124b896e03cc7e675e81ec445962396921d06cd9bdb2203b5383
120 Risk Score

Malware Insights

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

The file contains critical heuristic firings indicating the presence of Excel 4.0 macros that utilize WinAPI functions for downloading and executing files. Specifically, the macros appear to call functions like URLDownloadToFileA and ShellExecuteA, suggesting an intent to download and run a secondary payload. The absence of a document body means the rationale is based solely on the macro behavior and extracted WinAPI strings.

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