Office (OOXML) / .XLSX malware analysis — malicious · a3f2dda58a7e9406

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 62dfae450a8385f7da9ca2c4dcb33122 SHA-1: be2ba9dfc459cda13b3e39c1e24a632b0edfa912 SHA-256: a3f2dda58a7e94063ea986eb302bf880f438c46ebec19776a696bdabb2fa83d7

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. These macros are capable of executing arbitrary commands, which is a common technique for downloading and executing further malicious payloads. The macro content is heavily obfuscated and truncated, preventing a more detailed analysis of its specific actions or the reconstruction of any URLs or commands.

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` `af46294414fd23f8a2434ce2923f9fe32f9527c4cc01a9677d18b07977c239b4`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7582 bytes

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