Office (OOXML) / .XLSX malware analysis — malicious · f80ec3ea61438e7f

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: c3c5d898a932908c03e3f55d865e16fb SHA-1: c07b3610cd376993ac1815459e892af93b88df3a SHA-256: f80ec3ea61438e7fd99adc17fdc7631d4afeda803c04303607eb2b5938140b27

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros. The macros appear to be attempting to write a file to the filesystem at 'C:\ProgramData\fnsfunsgfgrgnkjfsgnd'. This is a common technique for dropping second-stage payloads. The exact functionality is difficult to determine due to obfuscation and truncation, but the intent is likely malicious code execution.

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` `299b2ec4a812d90e405488fb99b84df79ed902d8224cf73a04b91253b68cbaac`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	3458 bytes

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