Office (OOXML) / .XLSX malware analysis — malicious · cfaadec0b5c2da8e

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 8eb256976d455954eb8132e544ce06a5 SHA-1: 59345825dff5303d907f36960dff63d631086eb4 SHA-256: cfaadec0b5c2da8e9be09785d6d77401617a1ca8cde2fe21d7279a90d540d5d8

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 obfuscated strings that reconstruct to a file path, 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to write or execute a file from this location, likely as part of a multi-stage attack to download and run a secondary 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` `a6516ad631e5683322653ead8e73a84c3c54155ca3308ae9f0a5146079251827`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	186701 bytes

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