Office (OOXML) / .XLSX malware analysis — malicious · 486e887577e346ee

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 9b3768c1e2eacc3359f9f0b7f8216792 SHA-1: 9ec68d6a35b663096d1292cdadb4014c04c1d91d SHA-256: 486e887577e346ee0bef05224b02af94cef3fbf59d293180c246ffd0228e2ad6

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 macro sheet appears to be attempting to execute a file named 'excel.rtf' from the 'C:\ProgramData\' directory. This suggests the macro is designed to download and execute a second-stage payload. The exact functionality is difficult to determine due to truncation, but the presence of Excel 4.0 macros and the attempt to execute a file from a common download location strongly indicate a malicious downloader.

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` `85c1e72e1b88fd59f9eb35aee7f6c98c370545e1c9e584a72b10aeebc3adf3a4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	200062 bytes

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