Office (OOXML) / .XLSX malware analysis — malicious · e078ad4aebaf315f

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 0b88a47d1722a1ed9f26ecb64a7b4589 SHA-1: 1f99810ef922375afbda31cbc1cedf11c5072f39 SHA-256: e078ad4aebaf315f64b908917dbba9bc23e76387c3c1713fb565018f5850a8ac

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. The extracted macro code appears to be constructing a path to a file named 'excel.rtf' within the 'C:\ProgramData\' directory. This suggests the macro's purpose is to download and execute a second-stage payload from this location, likely as part of a broader attack chain.

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` `bc81e4d5695fdc680fd8b6a88de23fbb2673c3544890627a12602d3737ad3a98`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	591390 bytes

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