Office (OOXML) / .XLSX malware analysis — malicious · 289845bcbb865665

MALICIOUS

Office (OOXML) / .XLSX

77.9 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 9b26594b78af4cc59ea7f42ff9ce8887 SHA-1: cff2035d13ab45daebab25787eec6827d66cc0e4 SHA-256: 289845bcbb8656652fe2e9b4733b5bec16410b776cba3f6deacf75117d1683b6

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 the XLSX file. The extracted macro content, though truncated, reveals a path string that appears to be an attempt to execute a file from 'C:\ProgramData\excel.rtfB'. This suggests the macro's purpose is to download and execute a second-stage payload. Due to the truncated nature of the script, the exact execution mechanism and final payload remain unclear, leading to a moderate confidence score.

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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `52cab312d5b911a99fefcf201f8948235185bdc3ec7f854aee20640c8547fdf7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	130000 bytes

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