Office (OOXML) / .XLSX malware analysis — malicious · e50af3b956da19bc

MALICIOUS

Office (OOXML) / .XLSX

194.8 KB Created: 2021-10-14 17:24:36 UTC Authoring application: Microsoft Excel 12.0000

MD5: 8e63bc1a9cb6c158c3492769b5adeccb SHA-1: b233443dc04229842a734c7bcb21c02341efea20 SHA-256: e50af3b956da19bc450ad8f1edbf317d78391e031dd7c0d3e59a5eb469154ba6

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel document containing Excel 4.0 macros, as indicated by the OOXML_XLM_MACROSHEET heuristic. The embedded macro sheet, xlm_sheet_00.bin, is heavily obfuscated but its presence strongly suggests an attempt to execute arbitrary code. This is a common technique for downloading and executing further malicious payloads.

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` `bce455c8c7b00a8a1f1975c077490ffa88d3e64d1062261fed5258e2cf9b6584`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	346579 bytes

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