Office (OOXML) / .XLSX malware analysis — malicious · df9826201eea584e

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 5d1c6c264f92282f1290dd0230fc89d5 SHA-1: 4805775f9a20c3e033d5a94ec860a0ec085ae43d SHA-256: df9826201eea584e4e212f281f6f20677bb8cfebd9eb4e47bcc381b1edba698b

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The primary finding is the presence of an Excel 4.0 macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet contains obfuscated strings that reconstruct to 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 a first stage for downloading and running a secondary payload. The macro content is heavily truncated, preventing a more detailed analysis of its specific actions.

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` `f47080a93ad3c86f330f4e51d8d8b4c9234abb9c9c4ef06613814eb5f3f36802`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	101433 bytes

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