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

Static analysis result for SHA-256 81d14d41f08bef9f…

MALICIOUS

Office (OOXML) / .XLSX

181.3 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: e25879995154c065c9ebd68a693d29b9 SHA-1: eb5048d8ba45821a1a8a57840059c91f8d794c68 SHA-256: 81d14d41f08bef9ff184e023607eaf2407feb7deef773cb37a35b15500b8e051
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. Analysis of the macro sheet reveals a string concatenation that reconstructs the path 'C:\ProgramData\excel.rtf'. This suggests the macro's intent is to write a file to this location, likely as part of a multi-stage attack to download and execute a secondary 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
2a586f7fe858e45e1f2ea372d2859daba6b64b36b634f87b5142a88297c569b3		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 364115 bytes

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