Office (OOXML) / .XLSX malware analysis — malicious · 5ad8d2e74246232e

MALICIOUS

Office (OOXML) / .XLSX

371.0 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: e1c9c9c9322238b77b24f111d75bac15 SHA-1: 26e9a36ba99137d8dbf81f209f7266c609bde8f0 SHA-256: 5ad8d2e74246232eb387cba83196aeefc2e2d10ea8454445155227db28543db8

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 the XLSX file. These macros are known to be used for executing arbitrary commands, which is a common technique for downloading and executing further malicious stages. The macro content itself is heavily obfuscated and truncated, preventing a more detailed analysis of its specific actions or 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` `5c478cb53f54ad47ff7147ffcc247926ebf332cbabc900d771bee6c5eed352dc`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	608168 bytes

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