Office (OOXML) / .XLSX malware analysis — malicious · 43d08e34fdcb226a

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 91cd0de7d5078dd3645828e7159b0e11 SHA-1: da8c0fdeab056fabffb0756d9c9c7328d0d82dfc SHA-256: 43d08e34fdcb226a6d4b63cb0774718f933a522964791753db4336edd1d099ff

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. The macros appear to be designed to download and execute a second-stage payload, likely by creating a startup shortcut. The specific commands and URLs are heavily obfuscated within the macro sheet, making precise reconstruction difficult. However, the presence of macro execution and potential payload delivery strongly suggests a malicious intent.

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` `7af40dd5628fc69320ac2dd1153800fa67869ebda0f1b8ced9cad4fe2c628660`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	7745 bytes

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