Office (OOXML) / .XLSX malware analysis — malicious · 98640a38c5a55e97

MALICIOUS

Office (OOXML) / .XLSX

105.6 KB Created: 2021-03-29 19:55:34 UTC Authoring application: Microsoft Excel 16.0300

MD5: 653ae976b23e17981461345b9888416d SHA-1: 9532c79b027e171d5421e055852caf295a20f8b4 SHA-256: 98640a38c5a55e9774ab8f4e7146f9f0a34c1f88862d2f68124a0da6af4d470e

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The macrosheet content is heavily obfuscated and truncated, preventing a detailed analysis of its specific actions. However, the presence of Excel 4.0 macros strongly suggests an intent to execute arbitrary commands for downloading and running a secondary payload.

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` `11630a6785ddc458da83591e6c404ca109af584be71c6cfa00815dbdea2ee2c7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	95545 bytes

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