Office (OOXML) / .XLSX malware analysis — malicious · 98bc46a08efba8e3

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 24d188b5deb52d7517ee307c110c1687 SHA-1: 052046f41d1c35f8e2ba55f5207730e621011c06 SHA-256: 98bc46a08efba8e3e2ed017f5e3517a0f91cb63de1917b2259c7525bc293f542

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. Analysis of the macro sheet reveals embedded strings that appear to construct a file path, 'C:\ProgramData\excel.rtf'. This suggests the macro's intent is to write or execute a file from this location, likely as part of a download or execution chain. The macro content is heavily obfuscated and truncated, limiting further analysis of its precise actions.

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` `d86deee18ad6999885e8d2d0ecfcfbc1d423e1f5085bdda0790d35c55614e968`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	119887 bytes

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