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

Static analysis result for SHA-256 ca275c5f9ad1aca7…

MALICIOUS

Office (OOXML) / .XLSX

91.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: f5d49f1d180ec3b42f879d7d6ce16a66 SHA-1: aa536d53f48157890d41a6c3eeccf50e298b77f4 SHA-256: ca275c5f9ad1aca7959871759d9e9ecf54e9847e3009acfdbdf41211d1de7238
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The file is an Excel 4.0 macro-enabled XLSX file. The embedded macro sheet contains obfuscated commands that appear to construct a path to 'C:\ProgramData\excel.rtf'. This suggests the macro is intended to drop and execute a secondary payload. The macro's obfuscation and the use of a seemingly benign filename for the dropped payload are common evasion techniques.

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
8744493577d760a72794c524ca7fc6a85b0c5ea9bf3cc8c3e2ee002cba3ae0cb		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 285448 bytes

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