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

Static analysis result for SHA-256 1dd687b54dc7ee70…

MALICIOUS

Office (OOXML) / .XLSX

99.2 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 9d52e95d5da946e0e33630a61a97a48a SHA-1: ca8efb9450563b0ea7ca508bdea19ab4e4603165 SHA-256: 1dd687b54dc7ee7016191de79e5a9a3d72263bb7a038ffeb56c9cd83453b1a3a
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. The embedded macro sheet contains strings that appear to construct a path to 'C:\ProgramData\excel.rtf', suggesting the macro's purpose is to download and execute a second-stage payload from this location. The macro sheet is heavily obfuscated, limiting further analysis of its exact execution flow.

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
7f4c1e14716c19dbef92ed331fda95ed790e22cd4f5b37a0b09dbff3a9970674		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 186440 bytes

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