Office (OOXML) / .XLSX malware analysis — malicious · da8377477d7402e5

MALICIOUS

Office (OOXML) / .XLSX

633.6 KB Created: 2021-10-10 18:55:08 UTC Authoring application: Microsoft Excel 12.0000

MD5: 5aa5a4ad5d9a6c1fcf726d58bc701f90 SHA-1: 19fe6ab6f6bbe52d6311f27b153f8cc85e5270aa SHA-256: da8377477d7402e559d4b57c705181910759e59156e3da01ebec5547268716c7

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The macrosheet content is heavily truncated, preventing a detailed analysis of its specific actions. However, the presence of Excel 4.0 macros strongly suggests an attempt to execute arbitrary code.

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` `a17f1637302289441552e8e30350d38ceb9dd87d64a681ae566ce463604247a0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	1607456 bytes

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