Office (OOXML) / .XLSX malware analysis — malicious · 577130ce81164a10

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 26486665fb4c05b90381c1d0b47d7839 SHA-1: c9c498acbb7ea7bf67690bb20f28c3167e3b4f2a SHA-256: 577130ce81164a102abdc2838ac8c0464d7efcd47da4c31ecc7c1861263c0874

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 OOXML file. The extracted macro content, though partially obfuscated, contains a path that appears to be an attempt to execute a file from a specific directory. This suggests the macro is designed to launch a second-stage payload. The confidence is moderate due to the obfuscated nature of the macro content.

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` `cfad43dd35b2dc78ba0917d361a5dbed3f3917b9d2c00a4d6bb2dcee21043d94`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4704 bytes

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