Office (OOXML) / .XLSX malware analysis — malicious · 44e5a76d8908a4d8

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 9dd20565415cc69061129d4f66a9a8dd SHA-1: aee0d4f8769f6313762f766810811401cf387339 SHA-256: 44e5a76d8908a4d8f7576f359b18ab9e4f425ad11950d044c2f0366e0a9c8bea

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing a macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The extracted macro code contains a WMIC command that attempts to create and execute a file named 'excel.rtf' from the ProgramData directory. This suggests the document is a delivery mechanism for a secondary payload.

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` `f5e46dd3e18b5c9634dc5f16263662cf46c69b1ad68eac03413fe6bffde4982c`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	64801 bytes

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