Office (OOXML) / .XLSX malware analysis — malicious · 5d3c9aebb0cae9d7

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: ff3de89f9e606b48bf73980e98d6427b SHA-1: fb6d7596e27d8d4df006e9d4b53e709f6d419950 SHA-256: 5d3c9aebb0cae9d71e339df6dda52da6679ea1b95090eb51c66032f93516e800

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic T1203 Exploitation for Client Execution

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, often to download and execute further malicious stages. While the specific commands are truncated, the presence of XLM macros strongly suggests an attempt at client execution.

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` `0da4748b67800174699d5b68e9565796def786d9c8a7d4c17280f52295877431`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	599716 bytes

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