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

Static analysis result for SHA-256 af628f63a54b1948…

MALICIOUS

Office (OOXML) / .XLSX

67.7 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: a98746d29b2fd43f8f498cd2d4e6d9ef SHA-1: 9bac8cef85829d3590324b77f40a81cb3be189fd SHA-256: af628f63a54b194822b05d8034a4cebba398e2d0e37cbb5ae6cce39aea7cb32d
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic T1204.002 Malicious File

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. Analysis of the embedded macro reveals a command that utilizes 'wmic' to execute 'mshta' with a command to download and run a file named 'excel.rtf' from the ProgramData directory. This suggests the macro's primary purpose is to act as a downloader for 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.

FilenameKindSourceSize
xlm_sheet_00.bin
09a1833609bf773a7fa2023ac9956335185442be9b7d1bcbe4d20ad4d98a392e		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 162441 bytes

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