Office (OOXML) / .XLSX malware analysis — malicious · e70d5dda6d489da9

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: b2a17f98115eb64563fd32663ba5ff16 SHA-1: 24096606d3f253fdb7e2c38472e9def5d94a1318 SHA-256: e70d5dda6d489da9e0fd9123c2334ba98f9474b720aeac009ac489f7f9e5285b

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of an Excel 4.0 macro sheet, which is a known method for executing malicious code. The macro sheet contains obfuscated strings that reconstruct to a file path, 'C:\ProgramData\excel.rtf', suggesting the macro's purpose is to write and potentially execute a file from this location. This is a common technique for downloading and running a second-stage 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` `3e871b5bdc0ff78d751e1b79d83a5539dc3d8cd9dcc457c2f033e09e43ae900f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	263564 bytes

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