Office (OOXML) / .XLSX malware analysis — malicious · 43a98442d5650bdf

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 04007a0e50f3836a555f63df98dffea0 SHA-1: a7a571756fd9f932fcb8f672c1b27badb1a51d6a SHA-256: 43a98442d5650bdfc9e354d1bcf39dd3e65023be25dfaf0fc7f302f16f31a69e

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing a macro sheet, indicated by the OOXML_XLM_MACROSHEET heuristic. The extracted macro content is heavily obfuscated and truncated, making it difficult to determine the exact payload. However, the presence of Excel 4.0 macros strongly suggests an intent to execute arbitrary commands upon opening.

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` `d130612de7277169e67ef5fc54faab59a6534cd2471689f1d19f2ec1a45a12a1`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7374 bytes

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