Malicious Office (OOXML) / .XLSX — malware analysis report

Static analysis result for SHA-256 3c8d855aa728cb57…

MALICIOUS

Office (OOXML) / .XLSX

101.2 KB Created: 2021-03-29 19:56:22 UTC Authoring application: Microsoft Excel 16.0300
MD5: 251838c33724403230f2afde5adef616 SHA-1: 900e3ce2e93567ae61ad0bec62b2bf3cace78165 SHA-256: 3c8d855aa728cb57d1c99d1e8c1002bcc0461be793ba065d0ba6d95b4d847007
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 an XLSX file. While the macro content is truncated and heavily obfuscated, the structure suggests it is designed to execute commands and potentially download additional content. This is a common delivery mechanism for initial access.

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.

FilenameKindSourceSize
xlm_sheet_00.bin
75e160fe059593f46ec0ba3d334faa926ddb7061a392c39cc8f26cc5eec03add		 xlm-macrosheet OOXML XLM macro sheet: xl/macrosheets/sheet1.bin 91649 bytes

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