Office (OOXML) / .XLSX malware analysis — malicious · c81217dcb90d77e0

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 69feb292e5aca67074c266252f40a9a4 SHA-1: 9e43aaa53019298f020576baf334ceef9c9f9516 SHA-256: c81217dcb90d77e0848040eb766ee2f1c0ad2626423907ba6bde9dc7ef78cce0

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file identified as containing Excel 4.0 macros. The macro sheet appears to be constructing a path to a file named 'excel.rtf' within the 'C:\ProgramData\' directory. This suggests the macro's intent is to write or execute a file from this location, likely to download and run a second-stage payload. The specific file path 'C:\ProgramData\excel.rtf' is included as a potential IOC.

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` `b71894a69c7e58bd66ed9fe7fa327264c735eaef99301f082b44322e69eb8597`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	389062 bytes

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