Office (OOXML) / .XLSX malware analysis — malicious · 45a7d49bb0e67037

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 5dec2fd17c61bd9664f52620395618b3 SHA-1: d56a70853b5d819cdfe56388f6571b146ccd3495 SHA-256: 45a7d49bb0e6703786cfb825dc1b56628a3f4460d77f3eec0404e4c7abc49599

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros. The heuristic firing indicates the presence of these macros, which are often used to execute arbitrary commands or download further payloads. The macro content itself is heavily truncated and obfuscated, preventing a detailed analysis of its specific actions or IOCs. However, the presence of Excel 4.0 macros strongly suggests an intent to execute malicious code.

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` `ae539824d4549a426ecfb96e4313dc0bc52aa9a7b262eddae29b9af98bc5c6ea`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	617698 bytes

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