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

Static analysis result for SHA-256 f2b3673528cd89c8…

MALICIOUS

Office (OOXML) / .XLSX

82.6 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000
MD5: fa406d8c969cb7e5792c1efe39425d33 SHA-1: 4fc098acdb74526f3e80a68bccfb28c20d579e06 SHA-256: f2b3673528cd89c8bea09c8ad3b12d3d326164454c99809ee23d916b8fb32077
60 Risk Score

Malware Insights

MITRE ATT&CK
T1059.005 Visual Basic

The sample is an Excel 4.0 macro sheet, which is a strong indicator of malicious intent. The macro sheet contains obfuscated strings that, when reconstructed, appear to form a path to a file named 'excel.rtf' within the ProgramData directory. This suggests the macro is intended to download and execute a second-stage payload from a remote server, likely disguised as an RTF document.

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
cdd0959466c92a0f6808a9000a3082e80a2d6752db43e41b7233a97224dbd53b		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 96523 bytes

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