Office (OOXML) / .XLSX malware analysis — malicious · bd4fab81697f40bc

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 12ce7f78864e8b8d42f1e3a9d61eaddd SHA-1: 00165994bb66a255011690d2822ab5996b163b79 SHA-256: bd4fab81697f40bc4eaa2fc1dcee9bf5a5173a38c3d8b01d58dfef74fcc7e6e4

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.001 PowerShell

The sample is an Excel 4.0 macro sheet, which is a known vector for malware delivery. The extracted script contains a command that appears to be attempting to execute 'wmic process call create' to run a file named 'excel.rtf' from the 'C:\ProgramData\' directory. This suggests the macro is designed to download and execute a second-stage 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` `58e9f951913592dc957ccf46756d821bba36b5639afb11fc06f5c4b8755cbac9`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	150920 bytes

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