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

Static analysis result for SHA-256 e6df75d5f855d7cd…

MALICIOUS

Office (OOXML) / .XLSX

60.4 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 9a3d6fd334ac95b02d40d05827fbe92d SHA-1: fcbfbdd6230a2f32e89cdd538514dea73219086b SHA-256: e6df75d5f855d7cd27989931c0ac97bd59cbb155f97e5c9575785c278f3c76f5
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. The embedded macro sheet appears to contain obfuscated code that attempts to write a file to 'C:\ProgramData\excel.rtf'. This file is likely a second-stage payload. The macro's intent is to download and execute this payload.

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
d6f4938ebde65f6f99940a5bb2b702484c876ef8065cf5bf2e9d6371a76ecfee		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 166996 bytes

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