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

Static analysis result for SHA-256 299c89fe0cf1a206…

MALICIOUS

Office (OOXML) / .XLSX

85.8 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: 9afbfdfe10d645350ecb1464781e0e53 SHA-1: 3b0bc52c2fa2b8646d2807cdc05b8ee58cc3430e SHA-256: 299c89fe0cf1a206ae2803c8218eb190a9216fb75eee9c506764acfdef87c044
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file is an Excel 4.0 macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The macro sheet contains obfuscated strings that appear to construct a path to a file named 'Microsoft Excel.rtf' within the 'C:\ProgramData\' directory. This suggests the macro's purpose is to execute commands, likely to download and run a second-stage payload from that location. The family is unknown due to the lack of specific indicators.

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
d2b2286c7f5609220bf83684254e173effaff74ffafc4b154cd0fb295c909bd9		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 280030 bytes

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