Office (OOXML) / .XLSX malware analysis — malicious · 25528ab62b935d7b

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: e525ab78fdc841a840014bfffc6d285e SHA-1: 871766186f3c4927507e4db400c4891305579f1a SHA-256: 25528ab62b935d7b77a8b5b141620baa8891b1cc118da5d81dcdf9cecfe9bd42

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The embedded macro sheet appears to contain obfuscated strings that reconstruct to a file path, 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to execute commands, potentially to download and run a malicious payload from that location or to write a malicious file to it. The family is unknown due to the lack of specific indicators.

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` `6f46a21d3e50bb0bffd77387203c492dc1599bf86ecdfa2d95e2bb59168630bc`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	127882 bytes

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