Office (OOXML) / .XLSX malware analysis — malicious · 3bca203789985705

MALICIOUS

Office (OOXML) / .XLSX

111.5 KB Created: 2021-08-16 09:36:27 UTC Authoring application: Microsoft Excel 12.0000

MD5: 84ac93478b912474fde1b71b46c839b6 SHA-1: ba6e506fd920bee8ba69e2b29646b9412b74a6f8 SHA-256: 3bca20378998570595aaab0b5cd32f5b47e7c21a48724f722be4d7fcdf99398d

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The primary finding is the presence of Excel 4.0 macros within an XLSX file, flagged by a critical heuristic. While the macro content is truncated and heavily obfuscated, its presence strongly suggests an attempt to execute arbitrary code. The specific intent of the macro cannot be determined due to the truncation, but it is likely designed for malicious purposes such as downloading further payloads or establishing persistence.

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` `4efd666505e15406a6acc6a76b11defc49a2323c3baf9f284a4eae91257dd0ef`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	232579 bytes

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