Office (OOXML) / .XLSX malware analysis — malicious · c9fa7a8c2ac44adf

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 740f8fad4409804908f463b78947badb SHA-1: 8ce79d91eded6368f11e8a4e47cf9c7feed9f3ca SHA-256: c9fa7a8c2ac44adf4023f01d04b3aca400fa7780c3767c70adb432fb1445c2ac

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 heavily truncated and obfuscated, the presence of such macros is a strong indicator of malicious intent, often used for downloading and executing further stages of an attack. The file is classified as malicious with a risk score of 60.

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` `a954e520de0d5e42a64e8717f235b0a587c459496d542115f3dbfd591090addf`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	4105 bytes

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