Office (OOXML) / .XLSX malware analysis — malicious · 7a66a9bd6be977c8

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: ee462d51a60d6fc4dfbde669d3087965 SHA-1: 4c6ce99282abdda2b68e1507086091fd381a101b SHA-256: 7a66a9bd6be977c8477a910b448c05e06cdeeb10395af4c4429bb68982cb9453

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic for Applications

The sample is an Excel file containing an Excel 4.0 macro sheet, as indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet appears to be attempting to write a file to 'C:\ProgramData\excel.rtf' and execute it. The script content is heavily truncated, preventing a full analysis of its capabilities or the reconstruction of any URLs or further commands. However, the presence of an executable macro and the attempt to write and run a file strongly suggests a downloader or initial execution stage.

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` `b785c6f99602a57e5f8133ddca43125bf0902be4178287b12a483c28267c64fb`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	103809 bytes

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