Office (OOXML) / .XLSX malware analysis — malicious · 889a6331576437c3

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 91a67bf6464223d5fe1f774ef9f14008 SHA-1: c13ea2692d02ee7d47e7772751f9f660f6c91346 SHA-256: 889a6331576437c3c20d79a6c9ca25c2875e8080e4a030faf0b73ced20a12aeb

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet appears to contain a command to execute a file located at 'C:\ProgramData\excel.rtf', suggesting a downloader or initial execution stage. The exact functionality beyond this is unclear due to truncation.

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` `8b00cba8e401b007b4f4e1637c083e4d38029a80542d91cbd717dfae8202ffbb`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	94947 bytes

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