Office (OOXML) / .XLSX malware analysis — malicious · 4d276f93ac5b95e8

MALICIOUS

Office (OOXML) / .XLSX

123.6 KB Created: 2021-03-29 19:56:22 UTC Authoring application: Microsoft Excel 16.0300

MD5: 6ce81c098e1eaa1477b3bf484bd55e21 SHA-1: 6d8a18c31c119d4248d3021ba38b279ad55833ef SHA-256: 4d276f93ac5b95e8e9c16476c9a95fe08e5a1d61c399a5d57a7b6cb4720f50f6

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing a macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The extracted macro content is heavily obfuscated and truncated, making it difficult to determine the exact payload. However, the presence of Excel 4.0 macros strongly suggests an attempt to execute arbitrary commands upon opening the document.

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` `0e33a14072ebe1aa0fde40c261076210e8b30e2381e35d0c2cbb9c3db48b36e6`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	91649 bytes

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