Office (OOXML) / .XLSX malware analysis — malicious · 1e934ca2c6239bc4

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 4e1a65e86010658728ec3b2ff79219b4 SHA-1: b479acf9f998548d0096ccc66aa31ea883f9256f SHA-256: 1e934ca2c6239bc4dceac98b9ef10b9796c09e93fe21824c2344dd01fe12519d

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.003 Windows Command Shell

The sample is an Excel 4.0 macro sheet, which is a strong indicator of malicious intent. The embedded script uses 'wmic process call create' to execute 'mshta' with a specific file path, 'C:\ProgramData\excel.rtf'. This indicates the macro is designed to download and execute a second-stage payload from that location. The obfuscated nature of the script and the use of a common download/execution utility suggest a downloader or droppper functionality.

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` `90de1076a1e9f7d250dd3f45fc3fc0c06b2856affed6641bed0426a949345c5d`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	58461 bytes

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