Office (OOXML) / .XLSX malware analysis — malicious · 4b033ec1de6ef16b

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 74a46948774bc7b1d7664dd54f4f7a73 SHA-1: 49a6c5bb01334d95bddba9d14103bdb364fc8af6 SHA-256: 4b033ec1de6ef16b79adeed9ccd5c14d867babef169109174f4d82226bb86b82

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 an XLSX file. The macro sheet contains strings that appear to construct a file path, 'C:\ProgramData\excel.rtf', suggesting the macro's intent is to create or manipulate a file at this location, likely as part of a download and execution chain. The macro content is heavily obfuscated and truncated, preventing a more detailed analysis of its specific actions.

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` `62463053c72b61be17e581703834115c5924abff8e2192c970bcd4f8d64c95b4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	92109 bytes

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