Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 cafb9b0bea9dd914…

MALICIOUS

Office (OOXML) / .XLSX

86.2 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: e0d93cf7f06c976bb5ca98c3c23f5a2e SHA-1: b8faadee1ff61e8be15bb430e4bbb0b38f09c5ff SHA-256: cafb9b0bea9dd9143ae78d0b2a66ff82c471a89dad059ec536bd62f6d7de6aac
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file is an Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The embedded macro appears to be constructing a path to a file named 'Excel.rtf' within the 'C:\ProgramData\Microsoft\' directory. This suggests the macro's purpose is to write or execute a malicious file from this location, likely as a first-stage downloader.

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.

FilenameKindSourceSize
xlm_sheet_00.bin
3834dc6ce590b2caf284c7f342aed83c1a5303f4a3da90f00584fe43e19ab6a1		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 253837 bytes

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