Office (OOXML) / .XLSX malware analysis — malicious · c9dd90f19910dcef

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 56c014858ab43688d7b867ba977c1ecd SHA-1: 8a6765084ed75c7b55759f10964016963a152fa2 SHA-256: c9dd90f19910dcef08ff10afe57f41f715af1afdf764c54944a80e4816ee0324

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing Excel 4.0 macros. The macros appear to be designed to execute a command that writes a file to 'C:\ProgramData\excel.rtf' and then likely executes it. This is a common technique for downloading and running a second-stage payload. The specific file path 'C:\ProgramData\excel.rtf' is reconstructed from the macro content.

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` `ecfbff41761adbb554c3e7824a02e2c52dfec7a0166f6740279682f380192717`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	141880 bytes

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