Office (OOXML) / .XLSX malware analysis — malicious · a1324f4524269c69

MALICIOUS

Office (OOXML) / .XLSX

114.5 KB Created: 2021-02-03 15:28:44 UTC Authoring application: Microsoft Excel 16.0300

MD5: 1bdf40b5cc9e7ce696a02eeab3fe4acb SHA-1: 7d614b7c62dfc71ffe5c643de7876ebf297736e6 SHA-256: a1324f4524269c69f320c1d3b033671ba99cda4b9644c9ef84f4a9ebdbb3a36f

120 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The sample is an OOXML file containing disguised Excel 4.0 macros. The heuristics indicate that the macro sheet is stored under a disguised package path, suggesting an attempt to evade detection. The embedded macro content is heavily truncated and obfuscated, preventing a detailed analysis of its specific actions. However, the presence of Excel 4.0 macros is a strong indicator of malicious intent, often used for initial access or payload delivery.

Heuristics 2

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.
Excel 4.0 macro sheet stored under disguised package path critical OOXML_XLM_DISGUISED_RELATIONSHIP

OOXML package declares an xlMacrosheet relationship whose target is outside the canonical xl/macrosheets/ path. Excel follows the relationship type, while path-only scanners can miss the macro execution surface.

Extracted artifacts 1

Files carved from inside the sample during analysis.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `3fd2c5ac9f1339b006d4b8558a66e92632e93690860205c61803635b864cb6a6`	xlm-macrosheet	OOXML XLM macro sheet: xl/xls/sheet1.bin	1007414 bytes

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