Office (OOXML) / .XLSX malware analysis — malicious · 8ffa8a52992a0596

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 83c83c511aea0757caf68852ee24b63b SHA-1: a3ac758e1a13e70c6fb28035239dd7bc466ad54d SHA-256: 8ffa8a52992a0596b8ba1316355c1eefa7d9ab8d46c56eb96d1f06c031dc9055

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. While the script content is heavily obfuscated and truncated, the presence of these macros strongly suggests an attempt to execute arbitrary code. The file's purpose is likely malicious, potentially involving the download or execution of a secondary payload, though specific details are obscured.

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` `05e01b76a50cb0562ab5daf17bc0e4e0b7a62b991a27bddb366a5c32b9215a8c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	165854 bytes

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