Office (OOXML) / .XLSX malware analysis — malicious · 850ddc82095f90de

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 44f61e0088c4120924b71988567a26ad SHA-1: 2e6d4e0b723e351f5d6a1937ab94e70776298d17 SHA-256: 850ddc82095f90de967252a2812a19e1d5762c6ff3cd5d2a5a270ff49a70d5d4

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 embedded macro sheet contains strings that appear to construct a file path, 'C:\ProgramData\excel.rtf', suggesting an attempt to write or execute a file from this location. This is a common technique for downloading and executing second-stage payloads.

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` `a243f8aaab403660940dac62ab97126114e3e51a7e14d211249943672a66b50f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	529237 bytes

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