Office (OOXML) / .XLSX malware analysis — malicious · 8d1cbc4714c5669a

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 0997fee3c93350b35bbb7ee78f455963 SHA-1: c63f63d56ffa91f608369ff0b6810d8bff57c531 SHA-256: 8d1cbc4714c5669a9c5b6a5d9d618042495011ae87363476eb834045f08b3ef2

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 that appears to be an attempt to execute a file named 'excel.rft' from the 'C:\ProgramData\' directory. This suggests the macro's purpose is to download and execute a second-stage 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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `b142ef55450ba402a228eddc12274050ae226e788db39ba1acee25cfe1f8d9b7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	171910 bytes

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