Office (OOXML) / .XLSX malware analysis — malicious · 1fc7f23645166789

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 233a1a44e52ad5dee2ddafdff289cab4 SHA-1: 4c98c9a6679a9afa021fbbc05ff1ae16f848406a SHA-256: 1fc7f2364516678965e06403481a232e0e3fb96aaf413b5d3ea12c3ddbdf43f9

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1204.002 Malicious File

The sample is an Excel file containing a macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The macro sheet contains a command that uses `wmic` to execute `mshta` with a specific file path, 'C:\ProgramData\excel.rtf'. This indicates the macro's intent is to download and execute a second-stage payload from that location. The family is unknown due to the lack of specific indicators.

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` `482730a81d637ebde49d6335f1e894cc10fc1013807eb1851c9d38104b1036ec`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	67774 bytes

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