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

Static analysis result for SHA-256 f5e7a8a9ab398343…

MALICIOUS

Office (OOXML) / .XLSX

77.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: a8c07dffbc4cd9f1598b2f06fa74773c SHA-1: 50c169f5054410790ec76793ee2c699d47137992 SHA-256: f5e7a8a9ab398343c4ef660c7e84545fc1b0475f52196cff076c1ef6804fa1a2
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The primary finding is the presence of Excel 4.0 macros within an XLSX file, indicated by the OOXML_XLM_MACROSHEET heuristic. These macros are designed to execute arbitrary commands. The script content suggests an attempt to write a file to 'C:\ProgramData\excel.rtf', which is a common technique for dropping secondary payloads. The family is unknown due to the generic nature of the macro.

Heuristics 1

  • 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.

Extracted artifacts 1

Files carved from inside the sample during analysis.

FilenameKindSourceSize
xlm_sheet_00.bin
26073dbf00f5b8cd46732171d1d8a5c9156be53d6c8eab623a5fc908c5497da1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 127717 bytes

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