Office (OOXML) / .XLSX malware analysis — malicious · d3ca4b52094f2421

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 7c326adc553a434deecc489edbc4e41b SHA-1: fc362adf41606f0308ac4cc88ab7501d9a81f357 SHA-256: d3ca4b52094f242148d8ed2f3b4eaec94fe69d834c459f8c894de1f48ee489fb

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file contains Excel 4.0 macros, indicated by the OOXML_XLM_MACROSHEET heuristic. The macro sheet appears to be attempting to write an executable file named 'a.exe' to various common startup and program locations, suggesting a payload delivery or persistence mechanism. The exact commands are obfuscated within the macro sheet, but the pattern strongly suggests an attempt to download and execute 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` `3910218166d2a9b879da46fd0fdc58ee19b330090691bf26c85dbaa91d3e23ae`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4262 bytes

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