Office (OOXML) / .XLSX malware analysis — malicious · a8772e8b50936d7d

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 513ac26cbcad9afd633985a12ac124dd SHA-1: 1df47bbcecd8ecef4ceb2ea829386362dbd74832 SHA-256: a8772e8b50936d7dc98ee35a9e279b519ca4db1c195232ad3c758d16f83cca31

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 macros. The extracted macro commands reveal an attempt to execute 'wmic process call create' to run 'mshta' with a specific file path, 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to download and execute a second-stage payload disguised as an RTF file.

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` `a5c56cd0266841ca47ce3fe4b7ce38d3204d1a7d8634271172b52cdb7404ac47`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	57842 bytes

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