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

Static analysis result for SHA-256 b1d581ff101a801f…

MALICIOUS

Office (OOXML) / .XLSX

63.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 5c8e7435a6aa241e6b884873e3305184 SHA-1: 4aa2bd06c3542feb22b03d42fb736c9613ed1c57 SHA-256: b1d581ff101a801fe26e436612de42cc7f367852a251cd5274bcc3951d20a217
60 Risk Score

Malware Insights

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

The file is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The embedded macro uses 'wmic process call create' to execute a command-line utility. This utility is instructed to create a file named 'excel.rtf' in the 'C:\ProgramData\' directory. The macro's intent is to download and save a second-stage payload for 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.

FilenameKindSourceSize
xlm_sheet_00.bin
9c3dafba1b39698566bf42428bb3b0073b1f00e90867b6bbb2a58daf68f44357		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 93650 bytes

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