Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 c1786305c20b8787…

MALICIOUS

Office (OOXML) / .XLSX

67.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 090fe535dfd98800e4a8af0e68c2884e SHA-1: 553a3eec52cb04980f50ab5f7824130d170974ca SHA-256: c1786305c20b8787fe553c32dde3a0014ea020ec8cf5bf48eed137261431998c
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Service Execution: Service Execution

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet. Analysis of the macro content reveals a command that uses `wmic` to execute `mshta` and download a file from `C:\ProgramData\excel.rtf`. This suggests the macro's purpose is to download and execute a second-stage payload. The exact nature of the payload is not discernible from the provided evidence.

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.

FilenameKindSourceSize
xlm_sheet_00.bin
e249ff93a3fe51c933675f5481009f90996dbeaa6403a5c57f9250b45d890f5a		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 158180 bytes

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