Office (OOXML) / .XLSX malware analysis — malicious · 535b30cabebf8c40

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 65cbbb4aecdc222a7ee95b5030f74521 SHA-1: 5ca48859415f19c3b50b3874823b2ed78c19a08c SHA-256: 535b30cabebf8c4002315f8f666c985597fa01bc6400bb4ac5f57d4e0df25dba

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The critical heuristic firing indicates the presence of Excel 4.0 macros within the XLSX file. While the macro content is heavily obfuscated and truncated, the presence of such macros strongly suggests an attempt to execute arbitrary commands upon opening the document. This is a common technique for initial access and payload delivery.

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` `7a0c9098239302f86eeeb373c7897d9d46b33247990fc9755fbfd2403bcfea6e`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7939 bytes

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