Office (OOXML) / .XLSX malware analysis — malicious · 34b7091e57e91881

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: fadd22bf47bd1d1323d2eee65d469429 SHA-1: dd61e188a11a7c9addf97ca12ccdfcf45064297d SHA-256: 34b7091e57e91881530b0fee7a73e9cbcbfb32acffab0edfe1ef6f617b9b298a

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 the XLSX file. While the macro content is truncated and heavily obfuscated, the presence of such macros is a strong indicator of malicious intent, likely to download and execute a secondary payload or perform other harmful actions. The specific commands or URLs are not discernible from the provided excerpt.

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` `1f45b5740e85569d97f8a7f7b26727f561ac24bc0ceb146a129a46ef79c2223f`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	414650 bytes

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