Office (OOXML) / .XLSX malware analysis — malicious · b8ad0759ffced518

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 4f49f2a47564693157cdc4cc0c1378f0 SHA-1: 510ae044b29e57b34c52e3d53b699a0f9baa2cf8 SHA-256: b8ad0759ffced518e1a5810002b0aec258d2b9e47c1471b5f6067751fb860524

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Service Execution: Service Execution

The critical heuristic firing indicates the presence of Excel 4.0 macro sheets. The embedded script, though partially obfuscated, clearly shows a command to execute 'wmic process call create' with a specific file path 'C:\ProgramData\excel.rtf'. This suggests the macro's intent is to download and execute a second-stage payload from that location, likely to further compromise the system.

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` `c8a673833d5213bab9f81040ca1cf8b91a7ee298c7e893a9698a12d0fc254b9f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	69765 bytes

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