Office (OOXML) / .XLSX malware analysis — malicious · 1d968df283c7f915

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 055b847654deb7dea29f55588761c6b3 SHA-1: cc48517dcce901a4abf10ad63d0a6b945ae51a05 SHA-256: 1d968df283c7f9152326428f0ddc7f7b55e3bce9956c0ef016110ed385d5ecf4

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel spreadsheet containing Excel 4.0 macros, identified by the OOXML_XLM_MACROSHEET heuristic. The macro sheet appears to contain obfuscated strings that, when reconstructed, point to a file path 'C:\ProgramData\excel.rtf'. This suggests the macro's purpose is to execute commands, likely to download and run a secondary payload from this location. Due to the obfuscation and truncation, the exact execution flow cannot be fully determined, leading to a moderate confidence score.

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` `4bd89b010f125d7727505f0285f116747bb28adfd7b13d49176e094f166beed0`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	259021 bytes

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