Office (OOXML) / .XLSX malware analysis — malicious · cf341271ff548b33

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 64d652624a169eec6eb2b7e625c78ce1 SHA-1: 5a51b176301a8b1126aa29d7694247c6372fe62f SHA-256: cf341271ff548b335e196aa77aaaf60834c2b4fe79c8f27f6dfc80d30a9b0f8b

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet. The extracted macro content reveals a command that appears to be constructing a path, likely for dropping or executing a malicious payload. The reconstructed path is 'C:\ProgramData\fnsfunSfgRgnKjFsgNd'. This suggests the macro's primary function is to initiate the execution chain of a more complex attack.

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` `a02f015a55fd22cd0d2a962c13aef586b63bb7523044ef61eb0e7aacf1067a9e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4492 bytes

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