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

Static analysis result for SHA-256 bfd06d824a565020…

MALICIOUS

Office (OOXML) / .XLSX

24.5 KB Created: 2006-09-16 00:00:00 UTC Authoring application: Microsoft Excel 14.0300
MD5: db1a837ed46dd9076f570429cb30dd8b SHA-1: 7ad8af11f31add8b7db60be0df7496ded0c86037 SHA-256: bfd06d824a565020342eb0f7e4ee483ea96157a9d769987862aede3a72157285
120 Risk Score

Malware Insights

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

The file is an Excel 4.0 macro sheet, which is a known method for delivering malicious payloads. Heuristics indicate the presence of WinAPI calls such as URLDownloadToFileA and ShellExecuteA, strongly suggesting the macro's intent is to download and execute a second-stage payload from a remote location. The macro sheet also contains strings related to creating directories and specifying an .exe path, further supporting this conclusion. The exact download URL and executable path were not fully reconstructible from the truncated script.

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