Office (OOXML) / .XLSX malware analysis — malicious · a416127ec208d548

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 5362aaa4c79a021cf344364aff1a1673 SHA-1: cd4d19c0e88652e70ba19a6dfe5017e078212438 SHA-256: a416127ec208d54843753faaac0845a57315df41150733650dae7ef253ca6035

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 the XLSX file. The macro sheet contains a string that appears to be a directory path, 'C:\ProgramData\fnsfunsfgregnkjfsgnd', which is likely used to stage or execute malicious content. This suggests the macro's primary function is 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` `f1ea191e18da61c2a65f29393cd428356c7215c138bbd6083df81e89b3ad64f7`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	3654 bytes

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