Office (OOXML) / .XLSX malware analysis — malicious · 28dfcb4fedf6a37b

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: bf3b6215c6671e4074df687964db7043 SHA-1: 41f9b039883f9b44978f1b7e5a7fa0620a8718a7 SHA-256: 28dfcb4fedf6a37bd0fde6db10a1332a4d6c71a28a07ef36f5fd388ebb11c816

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The sample is an Excel file containing a macro sheet, identified by the OOXML_XLM_MACROSHEET heuristic. The extracted macro content is heavily truncated and obfuscated, making it impossible to determine the exact functionality or reconstruct specific IOCs. However, the presence of Excel 4.0 macros strongly suggests an intent to execute arbitrary code, likely for downloading and running a secondary payload.

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` `ec61b280454d054185c5b36e8c03cbd38f358124ce86605f6bb212a5699c76fd`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	273523 bytes

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