Office (OOXML) / .XLSX malware analysis — malicious · 7a12ee49d2fc7090

MALICIOUS

Office (OOXML) / .XLSX

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

MD5: 36a60a5aaf5fc521351ce68ad8491425 SHA-1: eb8e8354812d5db2078311b907d61602ba44a9e9 SHA-256: 7a12ee49d2fc7090bed511933372f4eede1b4df5b63c376b74cfde1b5e6f5c26

60 Risk Score

Malware Insights

MITRE ATT&CK

T1059.005 Visual Basic

The file is an Excel XLSX containing an embedded Excel 4.0 macro sheet. The macro sheet appears to be attempting to write a file to C:\ProgramData\excel.rtf, likely as a staging location for a second-stage payload. The macro sheet is heavily obfuscated, preventing a full analysis of its execution flow, but the presence of the macro sheet and the suspicious file path indicate a malicious intent to download and execute further stages.

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` `95ebeb9e6ecf722d5f71c75113ecc897dc6acba3da35464f74a21f38b3a75413`	xlm-macrosheet	OOXML XLM macro sheet: xl/macrosheets/sheet1.bin	276110 bytes

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