Office (OOXML) / .XLSX malware analysis — malicious · 3bf8bc75f8f23650

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: e5a51838eae3e43c3de36c099bf6523c SHA-1: 9c6620ca5a1b6a5e1c0e53c93c6e27269a9d2f6b SHA-256: 3bf8bc75f8f23650c36a706eac9d2ab371ec5e9c25b1559c8d1ae789955efaca

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 OOXML file. The extracted macro content, though partially truncated, reveals a path construction that strongly suggests the execution of arbitrary commands. Specifically, it appears to be constructing a path to 'C:\ProgramData\excel.rtf', which is likely used to download and execute a second-stage 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` `71cdaed5043b74e4fc9707411483b09e177ecd09c0c1144732d118d0a613a4f0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	100865 bytes

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