Office (OOXML) / .XLSX malware analysis — malicious · 97d1c8d5cdc6a75a

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: c7be836a18ab2f136955800e698254a0 SHA-1: 42d412d0dc4665d6689d86be05aad85949f84fc4 SHA-256: 97d1c8d5cdc6a75accc14c9df6e588c8c154e20488feeef2d542d7268a45903e

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, indicated by the 'OOXML_XLM_MACROSHEET' and 'OOXML_XLM_DISGUISED_RELATIONSHIP' heuristics. The embedded macro sheet content is heavily obfuscated and truncated, preventing a detailed analysis of its specific actions. However, the presence of disguised macros strongly suggests an attempt to execute malicious code upon opening.

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` `94707f6392390fbf645232ea532d200479c173acb4209f458ddb3908ebb95b19`	xlm-macrosheet	OOXML XLM macro sheet: xl/de/sheet1.bin	1007414 bytes

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