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

Static analysis result for SHA-256 50951458b7bf78cd…

MALICIOUS

Office (OOXML) / .XLSX

85.3 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 49f27e843bd0d7b96cf870b6a09aede6 SHA-1: d3320ab90b1e79907f9e56316e704122ca755793 SHA-256: 50951458b7bf78cd3a73f7f5f724135c2f83571ba7c8d839d69cece4a4a4e1c3
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within an XLSX file. The embedded macro sheet contains strings that appear to construct a path to 'C:\ProgramData\excel.rtf', suggesting an attempt to write or execute a file from this location. This is a common technique for downloading and executing secondary payloads.

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
19e1e1064b6371e9830e2fa71ab7ed3b86eea2fc36648a78fb9c09289b68fe87		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 176986 bytes

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