Office (OOXML) / .XLSX malware analysis — malicious · 43ec1540fb556ea6

MALICIOUS

Office (OOXML) / .XLSX

74.6 KB Created: 2021-03-15 18:20:11 UTC Authoring application: Microsoft Excel 16.0300

MD5: f03b26c370e7f561af1f1b6dfb4dff17 SHA-1: da0c77ee3d0f886d4da63f2365013a2203e23653 SHA-256: 43ec1540fb556ea63fce7a3148916399a5ebe9f4ca2a85d2539b87e734a641ff

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 presence of such macros strongly suggests an intent to execute arbitrary commands. The specific commands and their targets could not be fully reconstructed due to the truncated nature of the script.

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` `3b30b847ecb3aee3c97475515d4b1ac5ef6cb473175a1f0b3906a981ea7cf456`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	96434 bytes

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