Office (OOXML) / .XLSX malware analysis — malicious · 20a5f01c57b0c6e2

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 40d50a5f885a986d2cf2e3b8b39ffeb4 SHA-1: 0526733372168e2876e360283072c179f72c4773 SHA-256: 20a5f01c57b0c6e2431da3562e6bc2c546a620a97d3be73451a1699b277fc4e4

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 contain obfuscated commands that likely attempt to execute arbitrary code, potentially downloading and running a second-stage payload. The reconstructed path 'C:\ProgramData\excel.rtf' suggests an attempt to write or execute a file from a common location.

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` `67583ba9bdf074cd7754c77f1bc8a8b1573216eb981c3fbdb0abb9c46dbcab2b`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	535136 bytes

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