Office (OOXML) / .XLSX malware analysis — malicious · bc64eb93cd133670

MALICIOUS

Office (OOXML) / .XLSX

250.9 KB Created: 2021-04-07 06:31:40 UTC Authoring application: Microsoft Excel 16.0300

MD5: 9d39f307b0d6276450038cca7568b2cc SHA-1: 72d0c43d84791c50e600d85e6deb2b9021cf7056 SHA-256: bc64eb93cd133670e5e997bdee03928d2408281ed8f07142ee13371da5352f88

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros. These macros appear to be constructing paths to executable files, likely for downloading and executing a second-stage payload. The reconstructed paths suggest a pattern of dropping files in the public user directory.

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` `637fd03c61ba1037bf7060f895335e7c74ddbe433589ec56768eba8bdbb7b738`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	2959 bytes

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