Office (OOXML) / .XLSX malware analysis — malicious · a8ef27d9abb7d567

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: e512ab163a5abd0f574746dfaa7d7bd1 SHA-1: ecf491958e16aced052ba08cfd526d9cb8320316 SHA-256: a8ef27d9abb7d567c099e5355f69329035ce2131133b82f29c13877b0ed4bf74

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing a macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The extracted macro content reveals a command that uses 'wmic' to execute 'mshta' with a specific file path, 'C:\ProgramData\excel.rtf'. This indicates the macro's intent is to download and execute a second-stage payload from that location. The family is unknown due to the generic nature of the payload execution.

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` `2ad526f4fe4b635f03497762fa0811fef4426b8b0e8acc949741bbab2d0375da`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	163293 bytes

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