Office (OOXML) / .XLSX malware analysis — malicious · fffb63018d50e55c

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: e4e35a2204c0ffc3d84404892d83c541 SHA-1: 45eb414687d60c26e04eb165738d09d775529ce7 SHA-256: fffb63018d50e55c488d9f3a2ad8b0e646b5f973ad9d283a71e7821120487fbd

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel macro-enabled sheet (XLM) containing embedded macros. The heuristics indicate the presence of Excel 4.0 macros, which are often used for malicious purposes. The macro appears to be attempting to write a file to disk at 'C:\ProgramData\excel.rtf', likely as part of a download or execution chain for a second-stage payload. Due to the obfuscated nature of the macro content, the exact download URL or subsequent actions could not be definitively determined.

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` `4c9b0a571015dc719865c066ccec8cc234e156527d71776ef4988cb4626a02f5`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	138540 bytes

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