Office (OOXML) / .XLSX malware analysis — malicious · bbad1214d89fc321

MALICIOUS

Office (OOXML) / .XLSX

71.0 KB Created: 2021-03-15 18:19:36 UTC Authoring application: Microsoft Excel 16.0300

MD5: bd712f9de5fb81340b4e1eb8b98d35ac SHA-1: 3396987fc72af34a67b1fbbd49645a36cf324576 SHA-256: bbad1214d89fc321edb837f6eedae53d4efec53d3c2ee1b4549f066405a09b16

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 be obfuscated and truncated, but the presence of Excel 4.0 macros strongly suggests an intent to download and execute a secondary payload. Due to the obfuscation and truncation, the exact nature of the payload and its delivery mechanism cannot be confidently determined.

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` `cb02da0bdffd5b8826410fece42802ffaa2788cc3a67ee80f8cc43f88da42ec1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	93628 bytes

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