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

Static analysis result for SHA-256 f6891c049ad79460…

MALICIOUS

Office (OOXML) / .XLSX

78.5 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: d44d18b5e40002c7fcae488509af8982 SHA-1: 73a0e6f12bed1ef03003452e9c9d98c9da612ef5 SHA-256: f6891c049ad794609629a2cd0f88491c22d9977ff7653360be2d2bfcc4c1e9cd
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic 'OOXML_XLM_MACROSHEET' indicates the presence of Excel 4.0 macros. The embedded macro sheet contains strings that appear to construct a file path, 'C:\ProgramData\excel.rtf', suggesting the macro's purpose is to write or manipulate a file at this location, likely as part of a download or execution chain. The macro content is heavily obfuscated and truncated, preventing a more detailed analysis of its exact function.

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
85e6823154b6c0af7003148def14f9eca9754f79ae896f830945011c85a77d22		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 151451 bytes

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