Office (OOXML) / .XLSX malware analysis — malicious · 42089bb069d475ed

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: b70e425da0863dcd9fde1e02b8f49d5a SHA-1: 3706c1eee61d5dcb22c0898d94eca0c338f3b391 SHA-256: 42089bb069d475ed1937a2f6f112da38b56ffb07281d659cf63193bc0465a9f8

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 XLSX file. The extracted macro content, though truncated and partially obfuscated, appears to reference a file path 'C:\ProgramData\excel.rtf', suggesting an attempt to download and execute a secondary payload from this location. This is a common technique for initial access and further infection.

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` `b669ec0f499e62202784157760a436cf270aec950435b82751aa6c2f55fc4c78`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	113529 bytes

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