Office (OOXML) / .XLSX malware analysis — malicious · c1971b4959c69a2a

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 7c0beb9ebd03785037c6ea5afc81e28f SHA-1: 8721ff0ace2f67bcbbf6d91a0872186d865b4494 SHA-256: c1971b4959c69a2ace7c902969038af743316fa5ee9832469df9fc606f6fc4dd

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. While the macro content is truncated and heavily obfuscated, the structure suggests it is designed to download and execute a second-stage payload. The specific macro commands are not fully discernible due to truncation, preventing a more detailed analysis of the execution chain or specific IOCs.

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` `f93033fdbb256c9a12fba0fcf292b3f7d3cc2d6d00c00cd996dcf48e50a02be1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	91649 bytes

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