Office (OOXML) / .XLSX malware analysis — malicious · d9c2af3074265ca9

MALICIOUS

Office (OOXML) / .XLSX

83.3 KB Created: 2021-10-27 10:31:49 UTC Authoring application: Microsoft Excel 12.0000

MD5: 9b5a3cd2365594a324e5115d7d411445 SHA-1: 1ebcac796543f5cf5cc283ebccd8424f505dfd38 SHA-256: d9c2af3074265ca9dcb3bc6dfcdc5c62d15853f01810c84aec6c9e0e6fd1b9a1

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The embedded macro sheet contains obfuscated strings that appear to construct a file path, 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to write or execute a file from this location, likely as part of a multi-stage attack. The exact execution flow is unclear due to truncation, but the presence of the macro sheet strongly implies malicious intent.

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.

Filename	Kind	Source	Size
`xlm_sheet_00.bin` `0c040cefe498b0eea0efae333a19c4d34aeccf1b333ecdd5b4ae1fb1cb8513b0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	187483 bytes

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