Office (OOXML) / .XLSX malware analysis — malicious · dfdb40b966d61a7b

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 1a8c90c06421f5e693e3913a11272320 SHA-1: 24f22804f4f517ac9e0f1dda2c59d9fd5e4d936b SHA-256: dfdb40b966d61a7bfb2e1437a099815086218868df22180ab973152e30a9d555

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic 'OOXML_XLM_MACROSHEET' indicates the presence of Excel 4.0 macros. The extracted macro content, though truncated and partially obfuscated, contains a string that appears to be a file path: 'C:\ProgramData\fnsfunSfgRgnKjfsGnd'. This suggests the macro's purpose is to download and execute a second-stage payload from this location, which is a common technique for initial access and further infection.

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` `aa0939eafa0d7d3b53d005323aed20adbd02292459e20bfaa2cc62f22f1e8674`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4920 bytes

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